backend/headless: unconditionally accept all output layers

We don't need to do anything special to handle these.

backend/headless/output.c

@@ -2,6 +2,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <wlr/interfaces/wlr_output.h>
+#include <wlr/types/wlr_output_layer.h>
 #include <wlr/util/log.h>
 #include "backend/headless.h"
 
@@ -43,6 +44,12 @@ static bool output_test(struct wlr_output *wlr_output,
 		assert(state->mode_type == WLR_OUTPUT_STATE_MODE_CUSTOM);
 	}
 
+	if (state->committed & WLR_OUTPUT_STATE_LAYERS) {
+		for (size_t i = 0; i < state->layers_len; i++) {
+			state->layers[i].accepted = true;
+		}
+	}
+
 	return true;
 }