Match line length in row inversion with Image constructor

src/celengine/render.cpp

@@ -5535,6 +5535,7 @@ bool Renderer::captureFrame(int x, int y, int w, int h, PixelFormat format, unsi
     if (!gl::MESA_pack_invert)
     {
         int realWidth = w * formatWidth(format);
+        realWidth = (realWidth + 3) & ~0x3;
 #if defined(__GNUC__) && !defined(__STRICT_ANSI__)
         uint8_t tempLine[realWidth]; // G++ supports VLA as an extension
 #else