Fix C++ sleighexample

[ekilmer]

Commit 8fbd171 broke the example.

Steps to build the example:

git clone https://github.com/NationalSecurityAgency/ghidra
cd ghidra
gradle -I gradle/support/fetchDependencies.gradle init
gradle x86:sleighCompile
cd Ghidra/Features/Decompiler/src/decompile/cpp
make sleighexamp_dir
cd sleigh-2.1.0
make sleighexample

and then you can run it

./sleighexample disassemble
./sleighexample pcode
./sleighexample emulate

Found and fixed after having issues in lifting-bits/sleigh#245.

Related to:

• decompiler-cpp: Open sla files as 'binary' #6372
• decompiler-cpp: Add missing for-loop index variable check #6373