From c9b5cdca4290ebf58e620fe2af6e99fcd8e93b37 Mon Sep 17 00:00:00 2001
From: Manoj Bahuguna <manojbahugunamanoj@gmail.com>
Date: Thu, 4 Jul 2019 18:04:51 +0000
Subject: [PATCH] fix(useSize): prevents accessing iframe's property when it's
 not defined

ref #442
---
 src/useSize.tsx | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/useSize.tsx b/src/useSize.tsx
index 797bd08482..c488e76718 100644
--- a/src/useSize.tsx
+++ b/src/useSize.tsx
@@ -45,7 +45,13 @@ const useSize = (
   };
 
   useEffect(() => {
-    const iframe: HTMLIFrameElement = ref.current!;
+    const iframe: HTMLIFrameElement = ref.current;
+
+    if(!iframe) {
+      // iframe will be undefined if component is already unmounted
+      return;
+    }
+
     if (iframe.contentWindow) {
       window = iframe.contentWindow!;
       onWindow(window);