Perform early return in Log ctor.

src/lib/log.js

@@ -18,11 +18,11 @@ var EventEmitter = require('events').EventEmitter;
  */
 function Log(config) {
   config = config || {};
+  if (!config.log) return;
 
   var i;
   var outputs;
 
-  if (config.log) {
   if (_.isArrayOfStrings(config.log)) {
     outputs = [{
       levels: config.log
@@ -48,7 +48,6 @@ function Log(config) {
   for (i = 0; i < outputs.length; i++) {
     this.addOutput(outputs[i]);
   }
-  }
 }
 _.inherits(Log, EventEmitter);