Fonts without UTF8 characters do not compile

[SomeRanDev]

Whenever I use a font without utf8 characters, the assert at include/bn_sprite_font.h:119 fails at compile-time. It fixes itself if I add just a single utf8 character, so not a huge deal... but the assert message is very confusing, and it took me a bit to figure out what was happening, so figured I'd report.

To replicate, I've attached the font I'm using. Just drop in example project and the error will occur:
madou_futo_maru_gothic.zip

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Attaching error message to help anyone with similar error search for this

in 'constexpr' expansion of '((bn::sprite_font*)this)->bn::sprite_font::sprite_font((* & item), (* & utf8_characters_ref), (* & character_widths_ref), 0)'
butano/include/bn_assert.h:133:25: error: call to non-'constexpr' function 'void __assert_func(const char*, int, const char*, const char*)'
  133 |                         assert(condition); \
      |                         ^~~~~~
butano/include/bn_sprite_font.h:119:9: note: in expansion of macro 'BN_ASSERT'
  119 |         BN_ASSERT(character_widths_ref.empty() ||
devkitARM/arm-none-eabi/include/assert.h:41:6: note: 'void __assert_func(const char*, int, const char*, const char*)' declared here
   41 | void __assert_func (const char *, int, const char *, const char *)
      |      ^~~~~~~~~~~~~
make[2]: *** [/devkitARM/base_rules:39: FontLoader.o] Error 1
make[1]: *** [/butano/butano.mak:207: build] Error 2
make: *** [/butano/butano.mak:202: all] Error 2

[6TELOIV]

Getting the same error here.