From e7b00c46586b3c286a137e81d82af8843e488f6c Mon Sep 17 00:00:00 2001
From: Varun Dey <varundey20@gmail.com>
Date: Wed, 29 Jul 2020 15:22:48 +0000
Subject: [PATCH] Bug 1634988 - guard state against being undefined in
 BrowserElementParent. r=mconley

Differential Revision: https://phabricator.services.mozilla.com/D84896
---
 toolkit/actors/BrowserElementParent.jsm | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/toolkit/actors/BrowserElementParent.jsm b/toolkit/actors/BrowserElementParent.jsm
index 0f27b368de14..8798ea60333f 100644
--- a/toolkit/actors/BrowserElementParent.jsm
+++ b/toolkit/actors/BrowserElementParent.jsm
@@ -311,6 +311,11 @@ var PermitUnloader = {
   _transitionFrameState(windowGlobal, newFrameState) {
     let frameLoader = windowGlobal.rootFrameLoader;
     let state = this.inProgressPermitUnload.get(frameLoader);
+
+    if (!state) {
+      return;
+    }
+
     let oldFrameState = state.frameStates.get(windowGlobal);
 
     if (oldFrameState == STATE_WAITING) {