Fix validation of actions (and the validating text field itself).

Change-Id: I5a3bc9f0a7e3840f02e24cc9e2a919314b3df424
Fixes-Issue: CLIENT-438
Fixes-Issue: CLIENT-437
Reviewed-on: http://gerrit.dmdirc.com/3159
Reviewed-by: Chris Smith <chris@dmdirc.com>
Automatic-Compile: DMDirc Build Manager