small fix for 7944

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@42891 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/loader.c

@@ -199,6 +199,17 @@ struct ast_module_user *__ast_module_user_add(struct ast_module *mod,
 
 void __ast_module_user_remove(struct ast_module *mod, struct ast_module_user *u)
 {
+
+	if (u <= 0) {	
+		ast_log(LOG_ERROR,"ast_module_user invalid can not remove \n");		
+		return;
+	}
+
+	if (mod <= 0) {
+		ast_log(LOG_ERROR,"ast_module invalid can not remove \n");
+		return;
+	}
+	
 	AST_LIST_LOCK(&mod->users);
 	AST_LIST_REMOVE(&mod->users, u, entry);
 	AST_LIST_UNLOCK(&mod->users);