Wrong 404 behavior on taxonomy listing

No results ≠ 404.

404 must be returned when term does not exist. Not when not results are returned. 

If no results, template says "No posts for {{ term }}".
If term does not exist, then return a 404.
Merge remote-tracking branch 'upstream/master'
Changed abort message.
Test slug against array keys as options can be a slug => Label array
Fix auto-update of thumbnails after selecting from pull-down.
Nope, this should still be 'file'
Load fonts using the same protocol.
Also post record.id via preview functionality.
Merge pull request #2321 from xiaohutai/master

Also post record.id via preview functionality.
Even if we're not paging, we still need to provide a limit. Fixes #2319
ensure upload controller honours permissions
set the form to false if no permissions
use statements
hide ui
hide ui for files too
leave the add to stack button in place
allow editor to upload files
do not show upload if not allowed
mock the users object so that tests can run without permissions
Revert back to using span instead of button for now