fix NPE

Author: jacobg

src/android/QRScanner.java

@@ -777,7 +777,10 @@ public void run() {
             this.cordova.getActivity().runOnUiThread(new Runnable() {
                 @Override
                 public void run() {
-                    ((ViewGroup) mBarcodeView.getParent()).removeView(mBarcodeView);
+                    ViewGroup parent = (ViewGroup) mBarcodeView.getParent();
+                    if (parent != null) {
+                     parent.removeView(mBarcodeView);
+                    }
                     cameraPreviewing = false;
                 }
             });

src/common/src/createQRScannerAdapter.js

@@ -165,6 +165,7 @@ return {
       throw new Error('No callback provided to scan method.');
     }
     var success = function(result) {
+      // TODO: If there's an error code, then add message.
       callback(null, result);
     };
     cordova.exec(success, errorCallback(callback), 'QRScanner', 'scan', []);