Occasional segfaults when killing tabs

[AeroNotix]

No repro at the moment

[AeroNotix]

There's definitely something not right involved in killing tabs. Looks like sometimes the current webview can be assigned some invalid webview instance:

** (sbcl:16395): CRITICAL **: void webkit_web_view_stop_loading(WebKitWebView*): assertion 'WEBKIT_IS_WEB_VIEW(webView)' failed

** (sbcl:16395): CRITICAL **: WebKitFindController* webkit_web_view_get_find_controller(WebKitWebView*): assertion 'WEBKIT_IS_WEB_VIEW(webView)' failed

** (sbcl:16395): CRITICAL **: void webkit_find_controller_search_finish(WebKitFindController*): assertion 'WEBKIT_IS_FIND_CONTROLLER(findController)' failed

** (sbcl:16395): CRITICAL **: void webkit_web_view_stop_loading(WebKitWebView*): assertion 'WEBKIT_IS_WEB_VIEW(webView)' failed

** (sbcl:16395): CRITICAL **: void webkit_web_view_go_back(WebKitWebView*): assertion 'WEBKIT_IS_WEB_VIEW(webView)' failed