QmlJs: Fix yet another instance of QmlJsParser...

Same (!a == b) issue as everywhere else. Can we please unify all those
parsers? They all are slightly different though, at least this issue,
is never on the same line number.

Change-Id: Ie2d1540d47b848ed0c7596b3f309c046b64390cf
Reviewed-by: Lars Knoll <lars.knoll@digia.com>