[rmkit] interim fix for diacritic crashes

we no longer allow rendering at Y offsets below 0

src/rmkit/fb/stb_text.cpy

@@ -120,8 +120,14 @@ namespace stbtext:
        stbtt_GetCodepointHMetrics(&font, utf32[ch], &advance, &lsb);
        stbtt_GetCodepointBitmapBox(&font, utf32[ch], scale,scale,&x0,&y0,&x1,&y1);
 
-       offset := (baseline+y0) * image.w + (int)xpos + x0
        text_pos := (baseline + y0)*image.w + ((int) xpos + x0)
+
+       // if we go above the baseline, re-adjust the starting Y position to 0
+       // to prevent crashes.
+       // TODO: do this the correct way
+       if (baseline + y0) < 0:
+         text_pos = (int) xpos + x0
+
        stbtt_MakeCodepointBitmapSubpixel(&font, &text_buffer[text_pos], x1-x0,y1-y0, image.w, scale,scale,x_shift,0, utf32[ch]);
        // note that this stomps the old data, so where character boxes overlap (e.g. 'lj') it's wrong
        // because this API is really for baking character bitmaps into textures. if you want to render