Fix crash in ShowBookmarkBubble.

chrome/browser/ui/views/toolbar/toolbar_view.cc

Index: chrome/browser/ui/views/toolbar/toolbar_view.cc
diff --git a/chrome/browser/ui/views/toolbar/toolbar_view.cc b/chrome/browser/ui/views/toolbar/toolbar_view.cc
index d76088c3793a12325973360ed14eb9b10c67d4b3..249adb3ebfca349332c9b6eac7e22d5132ec3168 100644
--- a/chrome/browser/ui/views/toolbar/toolbar_view.cc
+++ b/chrome/browser/ui/views/toolbar/toolbar_view.cc
@@ -305,7 +305,7 @@ void ToolbarView::ShowBookmarkBubble(
   views::Widget* bubble_widget = BookmarkBubbleView::ShowBubble(
       anchor_view, gfx::Rect(), nullptr, observer, std::move(delegate),
       browser_->profile(), url, already_bookmarked);
-  if (star_view)
+  if (bubble_widget && star_view)
     bubble_widget->AddObserver(star_view);
 }