Updated stb_image to 2.12.

src/modules/graphics/opengl/Image.cpp

@@ -221,8 +221,8 @@ void Image::loadDefaultTexture()
 	setFilter(filter);
 
 	// A nice friendly checkerboard to signify invalid textures...
-	GLubyte px[] = {0xFF,0xFF,0xFF,0xFF, 0xFF,0xC0,0xC0,0xFF,
-	                0xFF,0xC0,0xC0,0xFF, 0xFF,0xFF,0xFF,0xFF};
+	GLubyte px[] = {0xFF,0xFF,0xFF,0xFF, 0xFF,0xA0,0xA0,0xFF,
+	                0xFF,0xA0,0xA0,0xFF, 0xFF,0xFF,0xFF,0xFF};
 
 	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 2, 2, 0, GL_RGBA, GL_UNSIGNED_BYTE, px);
 }