Validation missing when handling an ORTC exception

There's a validation missing on the gWebView object when handling an ORTC exception.
Causes the following exception:

```
Fatal Exception: java.lang.NullPointerException: Attempt to invoke interface method 'void org.apache.cordova.CordovaWebView.loadUrl(java.lang.String)' on a null object reference
at co.realtime.plugins.android.cordovapush.OrtcPushPlugin$13.run(OrtcPushPlugin.java:314)
```