fix: launcher kill method which was throwing an error if no callback …

…was specified

bug introduced in 8647266

In server.js when singleRun = true, no callback is passed to when a browser complete to launcher.kill so if a browser is not yet connected but one has already finished the process throw an error.

TypeError: undefined is not a function
    at process._tickCallback (node.js:415:13)

lib/launcher.js

@@ -53,7 +53,9 @@ var Launcher = function(emitter, injector) {
       }
     }
 
-    process.nextTick(callback);
+    if (callback) {
+      process.nextTick(callback);
+    }
     return false;
   };
 

test/unit/launcher.spec.coffee

@@ -96,6 +96,13 @@ describe 'launcher', ->
         expect(l.kill 'weid-id', done).to.equal false
         expect(browser.kill).not.to.have.been.called
 
+      it 'should not resolve callback if none was defined', (done) ->
+        l.launch ['Fake']
+        browser = FakeBrowser._instances.pop()
+
+        expect(l.kill 'weid-id').to.equal false
+        process.nextTick ->
+          done()
 
     describe 'killAll', ->
       exitSpy = null