app_server: blend last point in bilinear bitmap painting

We cannot just copy it in alpha overlay mode.

Change-Id: Icf494a1b1edc68a79b4298030be999fdf3a30c9a
Reviewed-on: https://review.haiku-os.org/c/haiku/+/11179
Haiku-Format: Haiku-format Bot <[email protected]>
Reviewed-by: waddlesplash <[email protected]>
Tested-by: Commit checker robot <[email protected]>

src/servers/app/drawing/Painter/bitmap_painter/DrawBitmapBilinear.h

@@ -310,7 +310,8 @@ struct BilinearDefault :
 		// pixel in bottom right corner if necessary
 		if (yMax < y2 && xIndexMax < xIndexR) {
 			const uint8* s = src + this->fWeightsX[xIndexR].index;
-			*(uint32*)d = *(uint32*)s;
+			uint32 t[4] = {s[0], s[1], s[2], s[3]};
+			DrawMode::Blend(d, &t[0]);
 		}
 	}
 };