My Files: don't check stream availability when URI is absent
My Files: don't check stream availability when URI is absent

Previously this was failing silently, but with the new error modals
it started popping up error messages.

akinwale/lbry-app,jsigwart/lbry-app,akinwale/lbry-app,jsigwart/lbry-app,lbryio/lbry-electron,akinwale/lbry-app,MaxiBoether/lbry-app,MaxiBoether/lbry-app,MaxiBoether/lbry-app,lbryio/lbry-app,lbryio/lbry-electron,jsigwart/lbry-app,MaxiBoether/lbry-app,jsigwart/lbry-app,lbryio/lbry-electron,lbryio/lbry-app,akinwale/lbry-app