ash: Add a NULL-check.

|phantom_widget_| used to be a scoped_ptr, and it used to .reset() itself here.
But it is a raw pointer now, so it needs to be null-checked.

BUG=none

Review URL: https://chromiumcodereview.appspot.com/10827205

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@150442 0039d316-1c4b-4281-b951-d872f2087c98

ash/wm/workspace/phantom_window_controller.cc

@@ -106,7 +106,8 @@ void PhantomWindowController::SetBounds(const gfx::Rect& bounds) {
 }
 
 void PhantomWindowController::Hide() {
-  phantom_widget_->Close();
+  if (phantom_widget_)
+    phantom_widget_->Close();
   phantom_widget_ = NULL;
 }