dont crash if callback isnt supplied to list methods

src/database/redis/list.js

@@ -2,34 +2,40 @@
 
 module.exports = function(redisClient, module) {
 	module.listPrepend = function(key, value, callback) {
+		callback = callback || function() {};
 		redisClient.lpush(key, value, function(err, res) {
 			callback(err);
 		});
 	};
 
 	module.listAppend = function(key, value, callback) {
+		callback = callback || function() {};
 		redisClient.rpush(key, value, function(err, res) {
 			callback(err);
 		});
 	};
 
 	module.listRemoveLast = function(key, callback) {
+		callback = callback || function() {};
 		redisClient.rpop(key, callback);
 	};
 
 	module.listRemoveAll = function(key, value, callback) {
+		callback = callback || function() {};
 		redisClient.lrem(key, 0, value, function(err, res) {
 			callback(err);
 		});
 	};
 
 	module.listTrim = function(key, start, stop, callback) {
+		callback = callback || function() {};
 		redisClient.ltrim(key, start, stop, function(err, res) {
 			callback(err);
 		});
 	};
 
 	module.getListRange = function(key, start, stop, callback) {
+		callback = callback || function() {};
 		redisClient.lrange(key, start, stop, callback);
 	};
 };