[#1260] Ignore "invalid return" error in onclick handler bu validator.nu.
html5validator manages for such code:
Throw following error:
Error: Bad value "window.location.reload(); return false;" for attribute "onclick" on element "input": invalid return
(The message itself originates fro Rhino.)
This contradicts JavaScript spec which allows to return (false) from handler
to cancel default widget's action. So, just disable such an error message.
