[mutter] test-utils: Fix compiler warning

[Jonas Ådahl <jadahl src gnome org>]

commit 446e82e86db3b4e0ea2fb84c8345983fbcfd56b8
Author: Hans de Goede <hdegoede redhat com>
Date:   Wed Jun 19 12:54:02 2019 +0200

    test-utils: Fix compiler warning
    
    This fixes the following compiler warning:
    
    In file included from /usr/include/glib-2.0/glib.h:114,
                     from ../src/tests/test-utils.h:23,
                     from ../src/tests/test-utils.c:22:
    ../src/tests/test-utils.c: In function ‘test_init’:
    /usr/include/glib-2.0/glib/glib-autocleanups.h:28:3: warning: ‘basename’ may be used uninitialized in 
this function [-Wmaybe-uninitialized]
       28 |   g_free (*pp);
          |   ^~~~~~~~~~~~
    ../src/tests/test-utils.c:73:24: note: ‘basename’ was declared here
       73 |       g_autofree char *basename;
          |                        ^~~~~~~~
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/627

 src/tests/test-utils.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/tests/test-utils.c b/src/tests/test-utils.c
index 980b20acd..a42005451 100644
--- a/src/tests/test-utils.c
+++ b/src/tests/test-utils.c
@@ -70,7 +70,7 @@ ensure_test_client_path (int    argc,
   if (!g_file_test (test_client_path,
                     G_FILE_TEST_EXISTS | G_FILE_TEST_IS_EXECUTABLE))
     {
-      g_autofree char *basename;
+      g_autofree char *basename = NULL;
       g_autofree char *dirname = NULL;
 
       basename = g_path_get_basename (argv[0]);