Fix crash when role is requested before widget is available

TBR=dfried@chromium.org

Bug: 952741
Change-Id: I2a5beb1c37f45e76fa5014be498ae1b80706dc75
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1577786
Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: Dana Fried <dfried@chromium.org>
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652937}
diff --git a/ui/views/window/dialog_delegate.cc b/ui/views/window/dialog_delegate.cc
index 9404c274..badb55d 100644
--- a/ui/views/window/dialog_delegate.cc
+++ b/ui/views/window/dialog_delegate.cc
@@ -246,6 +246,8 @@
 }
 
 DialogClientView* DialogDelegate::GetDialogClientView() {
+  if (!GetWidget())
+    return nullptr;
   return GetWidget()->client_view()->AsDialogClientView();
 }