gtk: Fix use after free

This undoes r132498, which I'm pretty sure was barking up the wrong tree.

The issue in the bug is that the model is cleared and the popup is /hidden/ (not destroyed), but still has events queued up. LineFromY does attempt to sanitize the result (in case the model has changed without the UI having a chance to catch up), but doesn't handle an empty model.

BUG=123530

Review URL: https://chromiumcodereview.appspot.com/23257002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@219636 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed