Prevent crash in NativeWidgetAura::IsMouseEventsEnabled() when no root window

ui/views/widget/native_widget_aura.cc

Index: ui/views/widget/native_widget_aura.cc
diff --git a/ui/views/widget/native_widget_aura.cc b/ui/views/widget/native_widget_aura.cc
index 4904f00c228f44d1686a8e7a59ee0e275e82fe82..0a6b3ab5daa80971ab3856a5b7594bfeb9a390c2 100644
--- a/ui/views/widget/native_widget_aura.cc
+++ b/ui/views/widget/native_widget_aura.cc
@@ -665,7 +665,7 @@ void NativeWidgetAura::SetCursor(gfx::NativeCursor cursor) {
 }
 
 bool NativeWidgetAura::IsMouseEventsEnabled() const {
-  if (!window_)
+  if (!window_ || !window_->GetRootWindow())
     return false;
   aura::client::CursorClient* cursor_client =
       aura::client::GetCursorClient(window_->GetRootWindow());