[pygobject] Add error-checking for the case where _arg_cache_new() fails

[Martin Pitt <martinpitt src gnome org>]

commit b4bef457c2d0ca6899e06a021f1f06252a37e326
Author: Dave Malcolm <dmalcolm redhat com>
Date:   Wed Jul 11 08:21:27 2012 +0200

    Add error-checking for the case where _arg_cache_new() fails
    
    This can happen when a typelib and its underlying library are out-of-sync. This
    converts the segfault into a more helpful traceback.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=678914

 gi/pygi-cache.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/gi/pygi-cache.c b/gi/pygi-cache.c
index 5083417..5d496d5 100644
--- a/gi/pygi-cache.c
+++ b/gi/pygi-cache.c
@@ -1277,6 +1277,8 @@ _args_cache_generate (GICallableInfo *callable_info,
                         return_direction,
                         -1,
                         -1);
+    if (return_cache == NULL)
+        return FALSE;
 
     return_cache->is_skipped = g_callable_info_skip_return (callable_info);
     callable_cache->return_cache = return_cache;