workaround jslint regression in https://github.com/douglascrockford/JSLint/commit/24f63ada2f9d7ad65afc90e6d949f631935c2480

git-svn-id: http://dev.piwik.org/svn/trunk@6561 59fd770c-687e-43c8-a1e3-f5a4ff64c105