Don't call swaynag_log for bg when not reading

sway/commands/output/background.c

@@ -110,7 +110,7 @@ struct cmd_results *output_cmd_background(int argc, char **argv) {
 		if (!can_access) {
 			wlr_log(WLR_ERROR, "Unable to access background file '%s': %s",
 					src, strerror(errno));
-			if (!config->validating) {
+			if (config->reading && !config->validating) {
 				swaynag_log(config->swaynag_command,
 						&config->swaynag_config_errors,
 						"Unable to access background file '%s'", src);