[mutter] renderer-native: Fix compiler warning

[Jonas Ådahl <jadahl src gnome org>]

commit 7fcdd60ac5d438a34916e793370a51e225281a54
Author: Hans de Goede <hdegoede redhat com>
Date:   Thu Jun 20 10:22:32 2019 +0200

    renderer-native: Fix compiler warning
    
    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;
          |                      ^~~~~~~
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/632

 src/backends/native/meta-renderer-native.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/backends/native/meta-renderer-native.c b/src/backends/native/meta-renderer-native.c
index 29a997c0f..31362cb19 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -770,7 +770,7 @@ pick_secondary_gpu_framebuffer_format_for_cpu (CoglOnscreen *onscreen,
       /* The rest are other fairly commonly used formats in OpenGL. */
       DRM_FORMAT_XRGB8888,
     };
-  g_autoptr (GArray) formats;
+  g_autoptr (GArray) formats = NULL;
   size_t k;
   unsigned int i;
   uint32_t drm_format;