Remove the destination file if trying to save a pixbuf failed

Fixes: https://bugzilla.gnome.org/show_bug.cgi?id=591102

gdk-pixbuf/gdk-pixbuf-io.c

@@ -2057,6 +2057,7 @@ gdk_pixbuf_savev (GdkPixbuf  *pixbuf,
        if (!result) {
                g_return_val_if_fail (error == NULL || *error != NULL, FALSE);
                fclose (f);
+               g_unlink (filename);
                return FALSE;
        }