Web Inspector: Crash closing a related tab with Web Inspector open while page is...

Web Inspector: Crash closing a related tab with Web Inspector open while page is refreshing
https://bugs.webkit.org/show_bug.cgi?id=145488

Reviewed by Alexey Proskuryakov.

* WebProcess/WebPage/WebInspector.h:
* WebProcess/WebPage/WebInspector.cpp:
(WebKit::WebInspector::~WebInspector):
Ensure, no matter how we close, that we have invalidated the
frontend connection of which we are the client.

(WebKit::WebInspector::createInspectorPage):
This member variable will never be null.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@185030 268f45cc-cd09-0410-ab3c-d52691b4dbfc