desktop/output: Skip repaint if wlr_output is disabled

When the repaint timer fires, we check if the sway_output is disabled,
and if so, skip the output commit after having reset frame_pending.

The sway_output enable flag is only updated if the output is disabled
and removed from the layout, not if the power is disabled for e.g. idle.
This can lead to situations where a commit is attempted on a disabled
output, which will lead to an attempted and failed primary swapchain
allocation.

Use the wlr_output.enabled state to check if the output is active.

sway/desktop/output.c

@@ -264,7 +264,7 @@ static int output_repaint_timer_handler(void *data) {
 	struct sway_output *output = data;
 
 	output->wlr_output->frame_pending = false;
-	if (!output->enabled) {
+	if (!output->wlr_output->enabled) {
 		return 0;
 	}