UnigramDev/Unigram/fasttext-fontsize-zero • f2a73c6 • 1 files, +9/-1
Fix crash when rendering the wallpaper preview bubbles

The plain-run fast path wrote whatever font size had changed, including 0, and
XAML rejects a FontSize of 0 with E_INVALIDARG. GetOrCreateRun already treats
non-positive as "inherit" and clears the property instead; the fast path now
does the same.

MessageBubble.Mockup reaches this: it calls SetText without a font size, so the
default of 0 replaces the size the bubble was previously rendered with, and the
transition is exactly what triggers the write.

Reported by crash telemetry on 12.9.0.0.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

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