[mutter/wip/carlosg/maybe-uninitialized: 2/3] compositor: Fix warning with -Wmaybe-uninitialized

[Carlos Garnacho <carlosg src gnome org>]

commit c8f43f1bcf448dda1ef5e72f797dc474def2db44
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri Dec 4 16:07:09 2020 +0100

    compositor: Fix warning with -Wmaybe-uninitialized
    
    Assert that the region is created, thus we passed a valid enum value
    to the get_scaled_region() function. Fixes:
    
      ../../../../Source/gnome/mutter/src/compositor/meta-surface-actor.c: In function ‘get_scaled_region’:
      ../../../../Source/gnome/mutter/src/compositor/meta-surface-actor.c:113:10: warning: ‘scaled_region’ 
may be used uninitialized in this function [-Wmaybe-uninitialized]
        113 |   return scaled_region;
            |          ^~~~~~~~~~~~~

 src/compositor/meta-surface-actor.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/src/compositor/meta-surface-actor.c b/src/compositor/meta-surface-actor.c
index e33b5a0360..48042b227d 100644
--- a/src/compositor/meta-surface-actor.c
+++ b/src/compositor/meta-surface-actor.c
@@ -83,7 +83,7 @@ get_scaled_region (MetaSurfaceActor     *surface_actor,
                    ScalePerspectiveType  scale_perspective)
 {
   MetaWindowActor *window_actor;
-  cairo_region_t *scaled_region;
+  cairo_region_t *scaled_region = NULL;
   int geometry_scale;
   float x, y;
 
@@ -107,6 +107,7 @@ get_scaled_region (MetaSurfaceActor     *surface_actor,
       break;
     }
 
+  g_assert (scaled_region != NULL);
   cairo_region_translate (region, -x, -y);
   cairo_region_translate (scaled_region, -x, -y);