Fix crash on clicking on <select> tag

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index d03257601681455b5cd3e03f793aa8e381b3b189..4733fce6a52a9a97c362eec7a31e748cc60af9f8 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -2460,9 +2460,11 @@ void RenderWidgetHostViewAura::UpdateCursorIfOverSelf() {
 }
 
 ui::InputMethod* RenderWidgetHostViewAura::GetInputMethod() const {
+  if (!window_)
+    return nullptr;
   aura::Window* root_window = window_->GetRootWindow();
   if (!root_window)
-    return NULL;
+    return nullptr;
   return root_window->GetHost()->GetInputMethod();
 }