From 4d5b25bf0e3b8fe111955461317462b1ae3c326d Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Thu, 24 Sep 2020 07:42:21 +0530
Subject: [PATCH] Fix #1896844 [Private
 bug](https://bugs.launchpad.net/calibre/+bug/1896844)

---
 src/pyj/iframe_comm.pyj | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/pyj/iframe_comm.pyj b/src/pyj/iframe_comm.pyj
index b06e58db0c..eb5589658e 100644
--- a/src/pyj/iframe_comm.pyj
+++ b/src/pyj/iframe_comm.pyj
@@ -206,6 +206,9 @@ class IframeClient:
                 print('Could not process message from parent:')
                 console.log(e)
                 return
+        if not data or not data.action:
+            console.log('Got a null message from parent in iframe, ignoring')
+            return
         func = self.handlers[data.action]
         if func:
             try: