remove 07_fix-NULL-username.patch, not applied anymore

debian/patches/07_fix-NULL-username.patch

@@ -1,18 +0,0 @@
---- a/src/lightdm-gtk-greeter.c
-+++ b/src/lightdm-gtk-greeter.c
-@@ -599,13 +599,13 @@ start_authentication (const gchar *usern
-     }
-     g_free (data);
- 
--    if (strcmp (username, "*other") == 0)
-+    if (g_strcmp0 (username, "*other") == 0)
-     {
-         gtk_widget_show (GTK_WIDGET (username_entry));
-         gtk_widget_show (GTK_WIDGET (cancel_button));
-         lightdm_greeter_authenticate (greeter, NULL);
-     }
--    else if (strcmp (username, "*guest") == 0)
-+    else if (g_strcmp0 (username, "*guest") == 0)
-     {
-         lightdm_greeter_authenticate_as_guest (greeter);
-     }