test: Fix null-argument issue in test_signals.c

Check if mountpoint is NULL before calling rmdir() in the error
path. This fixes CodeChecker warning about use of NULL 'mountpoint'
where non-null expected.

Reported by: CodeChecker (gcc-null-argument)

Signed-off-by: Bernd Schubert <bernd@bsbernd.com>

test/test_signals.c

@@ -72,7 +72,7 @@ static void fork_child(void)
 	/* Add the program name to arg[0] */
 	if (fuse_opt_add_arg(&args, "test_signals")) {
 		fprintf(stderr, "Failed to add argument\n");
-		goto out_free_mountpoint;
+		goto out_free;
 	}
 
 	/* Add debug flag to see more output */
@@ -82,14 +82,14 @@ static void fork_child(void)
 	mountpoint = strdup("/tmp/fuse_test_XXXXXX");
 	if (!mountpoint || !mkdtemp(mountpoint)) {
 		fprintf(stderr, "Failed to create temp dir\n");
-		goto out_free_args;
+		goto out_free;
 	}
 
 	/* Create session */
 	se = fuse_session_new(&args, &test_ll_ops, sizeof(test_ll_ops), NULL);
 	if (!se) {
 		fprintf(stderr, "Failed to create FUSE session\n");
-		goto out_free_mountpoint;
+		goto out_free;
 	}
 
 	/* Mount filesystem */
@@ -155,10 +155,11 @@ out_unmount:
 	fuse_session_unmount(se);
 out_destroy_session:
 	fuse_session_destroy(se);
-out_free_mountpoint:
-	rmdir(mountpoint);
-	free(mountpoint);
-out_free_args:
+out_free:
+	if (mountpoint) {
+		rmdir(mountpoint);
+		free(mountpoint);
+	}
 	fuse_opt_free_args(&args);
 	exit(1);
 }