res_pjsip_config_wizard: fix unload SEGV

If certain pjsip modules aren't loaded, the wizard causes a SEGV
when it unloads.  Added a check for the presense of the object
type wizard before trying to clean it up.

Tested-by: George Joseph
........

Merged revisions 429719 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@429720 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_pjsip_config_wizard.c

@@ -983,13 +983,14 @@ static int unload_module(void)
 			ao2_container_alloc_list(AO2_ALLOC_OPT_LOCK_NOLOCK, 0, NULL, NULL), ao2_cleanup);
 
 		otw = find_wizard(object_types[i]);
+		if (otw) {
 			if (otw->sorcery) {
 				ast_sorcery_instance_observer_remove(otw->sorcery, &observer);
 			}
-
 			otw->wizard->retrieve_multiple(otw->sorcery, otw->wizard_data, object_types[i], existing, NULL);
 			ao2_callback(existing, OBJ_NODATA | OBJ_UNLINK | OBJ_MULTIPLE, delete_existing_cb, otw);
 		}
+	}
 
 	AST_VECTOR_REMOVE_CMP_UNORDERED(&object_type_wizards, NULL, NOT_EQUALS, OTW_DELETE_CB);
 	AST_VECTOR_FREE(&object_type_wizards);