fix #2618 - dub run with targetType none fails with assert error instead of proper error message

[WebFreak001]

This only broke before in debug builds of dub / dub builds with asserts enabled. Luckily no functionality or logic needs to be changed, it's just a case of moving an assert down after an empty check and adding another empty check in a calling function, which makes the code logic more reasonable anyway.

[github-actions]

✅ PR OK, no changes in deprecations or warnings

Total deprecations: 15

Total warnings: 0

Build statistics:

 statistics (-before, +after)
 executable size=5524656 bin/dub
-rough build time=79s
+rough build time=78s

Full build output

DUB version 1.30.0, built on Feb 11 2023
LDC - the LLVM D compiler (1.31.0):
  based on DMD v2.101.2 and LLVM 14.0.3
  built with LDC - the LLVM D compiler (1.31.0)
  Default target: x86_64-unknown-linux-gnu
  Host CPU: skylake-avx512
  http://dlang.org - http://wiki.dlang.org/LDC

  Registered Targets:
    aarch64    - AArch64 (little endian)
    aarch64_32 - AArch64 (little endian ILP32)
    aarch64_be - AArch64 (big endian)
    amdgcn     - AMD GCN GPUs
    arm        - ARM
    arm64      - ARM64 (little endian)
    arm64_32   - ARM64 (little endian ILP32)
    armeb      - ARM (big endian)
    avr        - Atmel AVR Microcontroller
    bpf        - BPF (host endian)
    bpfeb      - BPF (big endian)
    bpfel      - BPF (little endian)
    hexagon    - Hexagon
    lanai      - Lanai
    mips       - MIPS (32-bit big endian)
    mips64     - MIPS (64-bit big endian)
    mips64el   - MIPS (64-bit little endian)
    mipsel     - MIPS (32-bit little endian)
    msp430     - MSP430 [experimental]
    nvptx      - NVIDIA PTX 32-bit
    nvptx64    - NVIDIA PTX 64-bit
    ppc32      - PowerPC 32
    ppc32le    - PowerPC 32 LE
    ppc64      - PowerPC 64
    ppc64le    - PowerPC 64 LE
    r600       - AMD GPUs HD2XXX-HD6XXX
    riscv32    - 32-bit RISC-V
    riscv64    - 64-bit RISC-V
    sparc      - Sparc
    sparcel    - Sparc LE
    sparcv9    - Sparc V9
    systemz    - SystemZ
    thumb      - Thumb
    thumbeb    - Thumb (big endian)
    ve         - VE
    wasm32     - WebAssembly 32-bit
    wasm64     - WebAssembly 64-bit
    x86        - 32-bit X86: Pentium-Pro and above
    x86-64     - 64-bit X86: EM64T and AMD64
    xcore      - XCore
   Upgrading project in /home/runner/work/dub/dub/
    Starting Performing "release" build using /opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/ldc2 for x86_64.
    Building dub 1.32.0-beta.1+commit.15.g8df81743: building configuration [application]
source/dub/internal/dyaml/node.d(2513,9): Deprecation: scope variable `this` assigned to non-scope parameter `_param_0` calling `match`
Serializing composite type Flags!(BuildRequirement) which has no serializable fields
Serializing composite type Flags!(BuildOption) which has no serializable fields
source/dub/dependency.d(917,18): Deprecation: scope variable `this` assigned to non-scope parameter `oth` calling `opEquals`
source/dub/dependency.d(920,30): Deprecation: scope variable `this` assigned to non-scope parameter `a` calling `doCmp`
source/dub/dependency.d(921,27): Deprecation: scope variable `this` assigned to non-scope parameter `b` calling `doCmp`
source/dub/dependency.d(939,26): Deprecation: scope variable `this` assigned to non-scope parameter `oth` calling `opEquals`
source/dub/internal/configy/Exceptions.d(130,34): Deprecation: reference to local variable `buffer` assigned to non-scope parameter `__anonymous_param` calling ``
source/dub/internal/configy/Exceptions.d(134,34): Deprecation: reference to local variable `buffer` assigned to non-scope parameter `__anonymous_param` calling ``
source/dub/internal/configy/Exceptions.d(248,27): Deprecation: `@safe` function `formatMessage` calling `formattedWrite`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/write.d(537,34):        which calls `std.format.spec.FormatSpec!char.FormatSpec.writeUpToNextSpec!(void delegate(in char[]) @safe).writeUpToNextSpec`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        which would be `@system` because of:
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        scope variable `this` assigned to non-scope parameter `e` calling `put`
source/dub/internal/configy/Exceptions.d(250,27): Deprecation: `@safe` function `formatMessage` calling `formattedWrite`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/write.d(537,34):        which calls `std.format.spec.FormatSpec!char.FormatSpec.writeUpToNextSpec!(void delegate(in char[]) @safe).writeUpToNextSpec`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        which would be `@system` because of:
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        scope variable `this` assigned to non-scope parameter `e` calling `put`
source/dub/internal/configy/Exceptions.d(283,27): Deprecation: `@safe` function `formatMessage` calling `formattedWrite`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/write.d(537,34):        which calls `std.format.spec.FormatSpec!char.FormatSpec.writeUpToNextSpec!(void delegate(in char[]) @safe).writeUpToNextSpec`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        which would be `@system` because of:
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        scope variable `this` assigned to non-scope parameter `e` calling `put`
source/dub/internal/configy/Exceptions.d(286,27): Deprecation: `@safe` function `formatMessage` calling `formattedWrite`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/write.d(537,34):        which calls `std.format.spec.FormatSpec!char.FormatSpec.writeUpToNextSpec!(void delegate(in char[]) @safe).writeUpToNextSpec`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        which would be `@system` because of:
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        scope variable `this` assigned to non-scope parameter `e` calling `put`
source/dub/internal/configy/Exceptions.d(323,31): Deprecation: `@safe` function `formatMessage` calling `formattedWrite`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/write.d(537,34):        which calls `std.format.spec.FormatSpec!char.FormatSpec.writeUpToNextSpec!(void delegate(in char[]) @safe).writeUpToNextSpec`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        which would be `@system` because of:
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        scope variable `this` assigned to non-scope parameter `e` calling `put`
source/dub/internal/configy/Exceptions.d(325,31): Deprecation: `@safe` function `formatMessage` calling `formattedWrite`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/write.d(537,34):        which calls `std.format.spec.FormatSpec!char.FormatSpec.writeUpToNextSpec!(void delegate(in char[]) @safe).writeUpToNextSpec`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        which would be `@system` because of:
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        scope variable `this` assigned to non-scope parameter `e` calling `put`
source/dub/internal/configy/Exceptions.d(332,31): Deprecation: `@safe` function `formatMessage` calling `formattedWrite`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/write.d(537,34):        which calls `std.format.spec.FormatSpec!char.FormatSpec.writeUpToNextSpec!(void delegate(in char[]) @safe).writeUpToNextSpec`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        which would be `@system` because of:
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        scope variable `this` assigned to non-scope parameter `e` calling `put`
source/dub/internal/configy/Exceptions.d(335,31): Deprecation: `@safe` function `formatMessage` calling `formattedWrite`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/write.d(537,34):        which calls `std.format.spec.FormatSpec!char.FormatSpec.writeUpToNextSpec!(void delegate(in char[]) @safe).writeUpToNextSpec`
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        which would be `@system` because of:
/opt/hostedtoolcache/dc/ldc2-1.31.0/x64/ldc2-1.31.0-linux-x86_64/bin/../import/std/format/spec.d(258,33):        scope variable `this` assigned to non-scope parameter `e` calling `put`
     Linking dub
STAT:statistics (-before, +after)
STAT:executable size=5524656 bin/dub
STAT:rough build time=78s

[Geod24]

Can you add a more descriptive commit / PR title ?

[WebFreak001]

done