added checking for new method

lib/logs.js

@@ -66,27 +66,29 @@ module.exports = {
 		// setup the stream filter correctly
 		return aliasGetAliasFunctionVersion
 		.then(version => {
-			return this.provider
-				.request('CloudWatchLogs',
-					'describeLogStreams',
-					params,
-					this.options.stage,
-					this.options.region)
-				.then(reply => {
-					if (!reply || _.isEmpty(reply.logStreams)) {
-						throw new this.serverless.classes
-							.Error('No existing streams for the function alias');
-					}
-					const logStreamNames = _.map(
-						_.filter(reply.logStreams, stream => _.includes(stream.logStreamName, `[${version}]`)),
-						stream => stream.logStreamName);
-
-					if (_.isEmpty(logStreamNames)) {
-						return BbPromise.reject(new this.serverless.classes
-							.Error('No existing streams for the latest version of function alias. If you want to view logs of a specific function version, please use --version to specify'));
-					}
-					return logStreamNames
-				});
+			if (version) {
+				return this.provider
+					.request('CloudWatchLogs',
+						'describeLogStreams',
+						params,
+						this.options.stage,
+						this.options.region)
+					.then(reply => {
+						if (!reply || _.isEmpty(reply.logStreams)) {
+							throw new this.serverless.classes
+								.Error('No existing streams for the function alias');
+						}
+						const logStreamNames = _.map(
+							_.filter(reply.logStreams, stream => _.includes(stream.logStreamName, `[${version}]`)),
+							stream => stream.logStreamName);
+
+						if (_.isEmpty(logStreamNames)) {
+							return BbPromise.reject(new this.serverless.classes.Error('No existing streams for the latest version of function alias. If you want to view logs of a specific function version, please use --version to specify'));
+						}
+						return logStreamNames;
+					});
+			}
+			return BbPromise.reject(new this.serverless.classes.Error('Function alias not found.'));
 		});
 
 	},