Fix the following compiler warning:
../src/backends/native/meta-renderer-native.c: In function ‘meta_renderer_native_create_view’:
/usr/include/glib-2.0/glib/gmacros.h:523:17: warning: ‘formats’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  523 |     { if (_ptr) (cleanup) ((ParentName *) _ptr); }                                                              \
      |                 ^
../src/backends/native/meta-renderer-native.c:773:22: note: ‘formats’ was declared here
  773 |   g_autoptr (GArray) formats;
      |                      ^~~~~~~

GNOME/mutter!632