LocalWindow::printErrorMessage(): check if frame is available.

If there's no frame, there's no console to add message to either.

R=haraken@chromium.org
BUG=376704

Review URL: https://codereview.chromium.org/413683002

git-svn-id: svn://svn.chromium.org/blink/trunk@178779 bbb929c8-8fbe-4397-9dbb-9b2b20218538