Barcode scanner: Fix failing scan result parsing

[marczych]

1. Go to the Media Manager.
2. Add an image from the Gallery.
3. A "Failed to parse result" toast is displayed but everything works as expected.

This is caused by the ZXing library parsing the Activity result but returning a null IntentResult because the request codes didn't match. The app didn't crash because the parsing code is all wrapped in a try/catch to swallow all errors because of the tricky reflection. This fixes the bug which removes the awkward Toast.