Problems with webkitgtk 2.36

Running luakit with any webkitgtk release in the 2.36 series as packaged on Arch Linux (tested against 2.36.0 through 2.36.7) leads to an assert failing when going back a page in the history. This happens with both the most recent tagged release and current `develop` commit.
```luakit --version
luakit 2.3.1
built with webkit 2.36.7 (installed version: 2.36.7)
```
```
luakit 2.3.1-4-ga8b1cd5c
built with webkit 2.36.7 (installed version: 2.36.7)
```
```
ERROR:widgets/webview.c:413:load_changed_cb: assertion failed: (!d->cert)
Bail out! ERROR:widgets/webview.c:413:load_changed_cb: assertion failed: (!d->cert)
```
I can reproduce this semi-consistently by going to https://www.archlinux.org, navigating to the forums, viewing any category, then hitting the previous page keybind or navigating back from the context menu, and happens with a completely stock config file.

There's also an issue with link hints not working on certain pages, but there aren't any visible errors to work from there, there are just no link hints created at all.

Start at widgets/webview.c:413 in load_changed_cb and reproduce the assertion with WebKitGTK 2.36.x by following the reported Arch Linux navigation sequence. Compare behavior with the stock configuration and test both back navigation and link hints on affected pages. Done means the assertion no longer occurs and the reported link-hint behavior is addressed or clearly characterized.

Written by the indexing model from the issue text.