Handle invalid handover URI

Fixes a case where the Nfc app would crash when asked to
send a non existing file.

How to reproduce:

1. Take a screenshot in any screen.
2. Launch [Photos].
3. Long-touch the image of step 1.
4. Tap the delete icon.
5. Tap [DELETE].
6. After deleting, pull down the status bar.
7. Tap the share icon of 'Screenshot captured'.
8. Tap [Android Beam].

Change-Id: I5b2a2cba49c3e68a94716bd28d6f5825903ace16