ash: Add a NULL-check.

ash/wm/workspace/phantom_window_controller.cc

Index: ash/wm/workspace/phantom_window_controller.cc
diff --git a/ash/wm/workspace/phantom_window_controller.cc b/ash/wm/workspace/phantom_window_controller.cc
index a33f0edbe07791d516c705aba63093f919952629..cebcb2a76510b77be63ce1207d55aa72a164dd5b 100644
--- a/ash/wm/workspace/phantom_window_controller.cc
+++ b/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;
 }