Check if BubbleReference weak pointer is valid before using it in the chooser

chrome/browser/ui/cocoa/website_settings/chooser_bubble_ui_cocoa.mm

Index: chrome/browser/ui/cocoa/website_settings/chooser_bubble_ui_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/website_settings/chooser_bubble_ui_cocoa.mm b/chrome/browser/ui/cocoa/website_settings/chooser_bubble_ui_cocoa.mm
index bf44f5637a14668ae6416eed713ef5c1d05599e7..dba5e9a55e40f79a0cc5deb0176220f02f2b0759 100644
--- a/chrome/browser/ui/cocoa/website_settings/chooser_bubble_ui_cocoa.mm
+++ b/chrome/browser/ui/cocoa/website_settings/chooser_bubble_ui_cocoa.mm
@@ -266,14 +266,16 @@ std::unique_ptr<BubbleUi> ChooserBubbleDelegate::BuildBubbleUi() {
 - (void)onConnect:(id)sender {
   buttonPressed_ = true;
   [chooserContentView_ accept];
-  self.bubbleReference->CloseBubble(BUBBLE_CLOSE_ACCEPTED);
+  if (self.bubbleReference)
+    self.bubbleReference->CloseBubble(BUBBLE_CLOSE_ACCEPTED);
   [self close];
 }
 
 - (void)onCancel:(id)sender {
   buttonPressed_ = true;
   [chooserContentView_ cancel];
-  self.bubbleReference->CloseBubble(BUBBLE_CLOSE_CANCELED);
+  if (self.bubbleReference)
+    self.bubbleReference->CloseBubble(BUBBLE_CLOSE_CANCELED);
   [self close];
 }