main/config_options: Check for existance of internal object before derefing

Asterisk can load and register an object type while still having an invalid
sorcery mapping. This can cause an issue when a creation call is invoked.
For example, mis-configuring PJSIP's endpoint identifier by IP address mapping
in sorcery.conf will cause the sorcery mechanism to be invalidated; however, a
subsequent ARI invocation to create the object will cause a crash, as the
internal type may not be registered as sorcery expects.

Merely checking for a NULL pointer here solves the issue.

Change-Id: I54079fb94a1440992f4735a9a1bbf1abb1c601ac

main/config_options.c

@@ -837,6 +837,10 @@ int aco_set_defaults(struct aco_type *type, const char *category, void *obj)
 	struct aco_option *opt;
 	struct ao2_iterator iter;
 
+	if (!type->internal) {
+		return -1;
+	}
+
 	iter = ao2_iterator_init(type->internal->opts, 0);
 
 	while ((opt = ao2_iterator_next(&iter))) {