Cursory testing seems to indicate that putting a newline character at the end of the list of Release Restrictions that contains at least one search items causes all searches to fail with a “Contains Restricted Term” notification. This is apparent on a Manual Search, and a silent fail on an Automatic or RSS search.
ie, the following will fail:
<…0 or more Search Items…>
<…Search Item…><…newline…>
<…eof…>
(Also, I don’t appear to be able to type a “T” or “t” in that box as the keystroke is captured and focus moves to the search box at the top of the window.)