I assumed that when load-committed signal is emitted for the main frame, the signals for the main resource had already been fired. That's indeed what happens when the page is normally loaded, but when the page is loaded from the backforward list, we don't even have a main resource when the loadcommitted signal is emitted.
Created attachment 152219 [details]
Patch to fix the crash, I'll file a new bug for the callbacks emisson order issue.
Thanks for the patch. If this patch contains new public API please make sure it follows the guidelines for new WebKit2 GTK+ API. See http://trac.webkit.org/wiki/WebKitGTK/AddingNewWebKit2API
Comment on attachment 152219 [details]
Committed r122567: <http://trac.webkit.org/changeset/122567>