[metacity] gradient: fix build warnings

[Alberts Muktupāvels <muktupavels src gnome org>]

commit abd35c18834bf4bd1645ef0f8eabf3bfe30cf724
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sun Sep 20 05:06:53 2015 +0300

    gradient: fix build warnings

 src/ui/gradient.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)
---
diff --git a/src/ui/gradient.c b/src/ui/gradient.c
index 39075f1..bb327ef 100644
--- a/src/ui/gradient.c
+++ b/src/ui/gradient.c
@@ -106,6 +106,9 @@ meta_gradient_create_simple (int              width,
                                             from, to);
     case META_GRADIENT_LAST:
       break;
+
+    default:
+      break;
     }
   g_assert_not_reached ();
   return NULL;
@@ -118,7 +121,6 @@ meta_gradient_create_multi (int              width,
                             int              n_colors,
                             MetaGradientType style)
 {
-
   if (n_colors > 2)
     {
       switch (style)
@@ -132,6 +134,9 @@ meta_gradient_create_multi (int              width,
         case META_GRADIENT_LAST:
           g_assert_not_reached ();
           break;
+        default:
+          g_assert_not_reached ();
+          break;
         }
     }
   else if (n_colors > 1)
@@ -836,5 +841,9 @@ meta_gradient_add_alpha (GdkPixbuf       *pixbuf,
     case META_GRADIENT_LAST:
       g_assert_not_reached ();
       break;
+
+    default:
+      g_assert_not_reached ();
+      break;
     }
 }