Hide thumbnail prview if no preview has loaded

In a case when a text is shared along with an image and image preview
has failed to load, text exclusion from sharing does not hides the text
but just greys it out (TextView marked disabled). This is to avoid
unpleasant collapsing animation, something we'd need to address
separately.

Bug: 274643406
Test: manual testing

Change-Id: I9fb9ce530afc1b31b2e075e15392bba256f36048
8 files changed