Fixes composite background option scaling incorrectly.

Fixes a bug where the composite background option would scale the filtered source incorrectly if the background source was a different size.

src/obs-composite-blur-filter.c

@@ -1815,6 +1815,7 @@ gs_texture_t *blend_composite(gs_texture_t *texture,
 		set_blending_parameters();
 		if (gs_texrender_begin(data->composite_render, data->width,
 				       data->height)) {
+			gs_ortho(0.0f, (float)data->width, 0.0f, (float)data->height, -100.0f, 100.0f);
 			while (gs_effect_loop(composite_effect, "Draw"))
 				gs_draw_sprite(texture, 0, data->width,
 					       data->height);
@@ -1825,4 +1826,4 @@ gs_texture_t *blend_composite(gs_texture_t *texture,
 		gs_blend_state_pop();
 	}
 	return texture;
-}
+}