Fix minor mistake - only increase size of compositing when stencil -is-

set.

source/blender/gpu/intern/gpu_compositing.c

@@ -291,7 +291,7 @@ bool GPU_fx_compositor_initialize_passes(
 
 	/* scissor is missing when drawing offscreen, in that case, dimensions match exactly. In opposite case
 	 * add one to match viewport dimensions */
-	if (!scissor_rect) {
+	if (scissor_rect) {
 		w++, h++;
 	}