Fix #8731: Always use a 32bpp blitter if font anti-aliasing is enabled.

src/gfxinit.cpp

@@ -268,6 +268,8 @@ static bool SwitchNewGRFBlitter()
 		if (c->status == GCS_DISABLED || c->status == GCS_NOT_FOUND || HasBit(c->flags, GCF_INIT_ONLY)) continue;
 		if (c->palette & GRFP_BLT_32BPP) depth_wanted_by_grf = 32;
 	}
+	/* We need a 32bpp blitter for font anti-alias. */
+	if (HasAntialiasedFonts()) depth_wanted_by_grf = 32;
 
 	/* Search the best blitter. */
 	static const struct {