Reviewed by Kevin Decker.

        Don't crash or hang when we fail to instantiate a plug-in.
        
        * Plugins/Hosted/NetscapePluginHostManager.mm:
        (WebKit::NetscapePluginHostManager::instantiatePlugin):
        Return 0 on failure.
        
        * Plugins/Hosted/WebHostedNetscapePluginView.mm:
        (-[WebHostedNetscapePluginView JSC::Bindings::createPluginBindingsInstance:JSC::Bindings::]):
        Null check for the proxy member.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@40127 268f45cc-cd09-0410-ab3c-d52691b4dbfc