Fix bug that would occure if process.env.DEBUG is a non-string value.

src/debug.js

@@ -141,7 +141,7 @@ function enable(namespaces) {
   exports.names = [];
   exports.skips = [];
 
-  var split = (namespaces || '').split(/[\s,]+/);
+  var split = (typeof namespaces === 'string' ? namespaces : '').split(/[\s,]+/);
   var len = split.length;
 
   for (var i = 0; i < len; i++) {

test/debug_spec.js

@@ -6,11 +6,11 @@ var chai
   , debug
   , sinon
   , sinonChai;
-  
+
 if (typeof module !== 'undefined') {
   chai = require('chai');
   expect = chai.expect;
-  
+
   debug = require('../src/index');
   sinon = require('sinon');
   sinonChai = require("sinon-chai");
@@ -20,28 +20,32 @@ if (typeof module !== 'undefined') {
 
 describe('debug', function () {
   var log = debug('test');
-  
+
   log.log = sinon.stub();
-  
+
   it('passes a basic sanity check', function () {
     expect(log('hello world')).to.not.throw;
   });
 
+  it('allows namespaces to be a non-string value', function () {
+    expect(debug.enable(true)).to.not.throw;
+  });
+
   context('with log function', function () {
-        
+
     beforeEach(function () {
       debug.enable('test');
       log = debug('test');
     });
-  
+
     it('uses it', function () {
       log.log = sinon.stub();
       log('using custom log function');
 
       expect(log.log).to.have.been.calledOnce;
     });
   });
-  
+
   describe('custom functions', function () {
     var log;
 
@@ -59,4 +63,5 @@ describe('debug', function () {
       });
     });
   });
+
 });