[vala] Fix build with -Werror=switch

[Rico Tzschichholz <ricotz src gnome org>]

commit efc507fd12eb8453363f03b7a2756dfa5c308a05
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Tue Jan 10 12:18:49 2017 +0100

    Fix build with -Werror=switch

 gobject-introspection/gidlnode.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/gobject-introspection/gidlnode.c b/gobject-introspection/gidlnode.c
index 6238366..8ad5c96 100644
--- a/gobject-introspection/gidlnode.c
+++ b/gobject-introspection/gidlnode.c
@@ -787,6 +787,8 @@ g_idl_node_can_have_member (GIdlNode    *node)
     case G_IDL_NODE_STRUCT:
     case G_IDL_NODE_UNION:
       return TRUE;
+    default:
+      break;
     };
   return FALSE;
 }