GSHorizontalTypesetter improvements: Handle Missing Fonts Gracefully

[IOOI-SqAR]

I asked the Kimi AI how to further improve GSHorizontalTypesetter. Here is what it came up with:

https://www.kimi.com/share/19d34cdb-8242-8fc9-8000-00001fd46e3b

Handle Missing Fonts Gracefully

// CURRENT: No check if currentFont is nil
lineHeight = [glyphCache->font defaultLineHeightForFont];

// PROPOSED:
if (!glyphCache->font) {
    // Use system default font as fallback
    currentFont = [NSFont systemFontOfSize: 12.0];
    // Log warning in debug builds
    NSDebugLLog(@"GSHorizontalTypesetter", @"Missing font at glyph %u, using system default", cacheBase);
}

[rmottola]

Fred commented privately this should be useless.