[Mac] Fix crash when closing window if the devtools process was killed.

Similar to http://crbug.com/237823.

BUG=244259

Review URL: https://chromiumcodereview.appspot.com/15706007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@202700 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/ui/cocoa/browser_window_controller.mm

@@ -665,7 +665,7 @@ enum {
     if (devtoolsWindow) {
       RenderWidgetHostView* devtoolsView =
           devtoolsWindow->web_contents()->GetRenderWidgetHostView();
-      if (devtoolsView->HasFocus()) {
+      if (devtoolsView && devtoolsView->HasFocus()) {
         devtoolsView->SetActive(false);
         return;
       }