[gnome-builder] editor: fix a warning

[Yosef Or Boczko <yoseforb src gnome org>]

commit 1833bf0b58a8eb13f39ba4cba0b48f1dbfa57a67
Author: Yosef Or Boczko <yoseforb src gnome org>
Date:   Mon Dec 15 17:47:34 2014 +0200

    editor: fix a warning

 src/editor/gb-editor-document.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/editor/gb-editor-document.c b/src/editor/gb-editor-document.c
index 198131f..86778fc 100644
--- a/src/editor/gb-editor-document.c
+++ b/src/editor/gb-editor-document.c
@@ -94,7 +94,7 @@ gb_editor_document_new (void)
 static gboolean
 gb_editor_document_is_untitled (GbDocument *document)
 {
-  g_return_val_if_fail (GB_IS_EDITOR_DOCUMENT (document), NULL);
+  g_return_val_if_fail (GB_IS_EDITOR_DOCUMENT (document), FALSE);
 
   return (GB_EDITOR_DOCUMENT (document)->priv->doc_seq_id > 0);
 }