[dia] [scan-build] Division by zero (not really)

[Hans Breuer <hans src gnome org>]

commit 9248aa802ff93a8e78d012e9f6ba8ab789b86065
Author: Hans Breuer <hans breuer org>
Date:   Sun Dec 6 16:15:49 2009 +0100

    [scan-build] Division by zero (not really)
    
    Check another pathologic case - having at leat one layer is
    as guaranteed as dia->data->active_layer!=NULL

 app/undo.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/app/undo.c b/app/undo.c
index 9a3d634..4b30667 100644
--- a/app/undo.c
+++ b/app/undo.c
@@ -1214,6 +1214,7 @@ move_object_layer_relative(Diagram *dia, GList *objects, gint dist)
   guint pos;
  
   g_return_if_fail(dia->data->active_layer);
+  g_return_if_fail(dia->data->layers->len != 0);
 
   active =  dia->data->active_layer;
   for (pos = 0; pos < dia->data->layers->len; ++pos)