Sharesheet - Check number of uris being shared

It's possible to use SEND_MULTIPLE while only sending 1 item.
Adjust the text in this case so that we don't show:
"{fileName} + 0 files".

Better handle errors when attempting to extract file names
and thumbnails.

Bug: 120419296
Test: atest ChooserActivityTest
Change-Id: Ib381974ffbf61c98031ada287bf2533172e6cf9f