Fix crash in widget destruction

ui/views/accessibility/ax_widget_obj_wrapper.cc

Index: ui/views/accessibility/ax_widget_obj_wrapper.cc
diff --git a/ui/views/accessibility/ax_widget_obj_wrapper.cc b/ui/views/accessibility/ax_widget_obj_wrapper.cc
index 70307b919d3e93b1d60cbc41593722767c4d1adf..2d96f8c9400ae7c5aef7beb37385384395b92871 100644
--- a/ui/views/accessibility/ax_widget_obj_wrapper.cc
+++ b/ui/views/accessibility/ax_widget_obj_wrapper.cc
@@ -32,8 +32,10 @@ AXAuraObjWrapper* AXWidgetObjWrapper::GetParent() {
 
 void AXWidgetObjWrapper::GetChildren(
     std::vector<AXAuraObjWrapper*>* out_children) {
-  if (!widget_->IsVisible() || !widget_->GetRootView()->visible())
+  if (!widget_->IsVisible() || !widget_->GetRootView() ||
+      !widget_->GetRootView()->visible()) {
     return;
+  }
 
   out_children->push_back(
       AXAuraObjCache::GetInstance()->GetOrCreate(widget_->GetRootView()));