[babl] Fix crash if failing to normalize path for loading extensions

[Jon Nordby <jonnor src gnome org>]

commit e045df0e05e8351fedeef856c8843262103f1085
Author: Jon Nordby <jononor gmail com>
Date:   Fri Jul 18 18:00:20 2014 +0200

    Fix crash if failing to normalize path for loading extensions
    
    Can for instance happen when running with "BABL_PATH=something:",
    which easily happens in scripts on form BABL_PATH=something:${BABL_PATH}

 babl/babl-extension.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/babl/babl-extension.c b/babl/babl-extension.c
index d021914..7626867 100644
--- a/babl/babl-extension.c
+++ b/babl/babl-extension.c
@@ -332,8 +332,10 @@ babl_extension_load_dir_list (const char *dir_list)
           case BABL_PATH_SEPARATOR:
           {
             char *expanded_path = expand_path (path);
-            babl_extension_load_dir (expanded_path);
-            babl_free (expanded_path);
+            if (expanded_path) {
+                babl_extension_load_dir (expanded_path);
+                babl_free (expanded_path);
+            }
           }
             dst = path;
             src++;