[gtksourceview] Fix crash on win32 with the guess_language func.

[Ignacio Casal Quinteiro <icq src gnome org>]

commit 5a4d0012aed72b7a9acffb825b7b019a6f7d601c
Author: Ignacio Casal Quinteiro <icq gnome org>
Date:   Wed Nov 18 18:32:38 2009 +0100

    Fix crash on win32 with the guess_language func.

 gtksourceview/gtksourcelanguagemanager.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/gtksourceview/gtksourcelanguagemanager.c b/gtksourceview/gtksourcelanguagemanager.c
index 2d30a45..f4e3ddb 100644
--- a/gtksourceview/gtksourcelanguagemanager.c
+++ b/gtksourceview/gtksourcelanguagemanager.c
@@ -539,7 +539,9 @@ pick_lang_for_mime_type (GtkSourceLanguageManager *lm,
 		GSList *langs;
 		
 		langs = pick_langs_for_filename (lm, alt_filename);
-		lang = GTK_SOURCE_LANGUAGE (langs->data);
+		
+		if (langs != NULL)
+			lang = GTK_SOURCE_LANGUAGE (langs->data);
 	}
 	
 	if (lang == NULL && mime_type != NULL)