check for body before attaching to body in response to error in build…

… found on CT, see #1048
phetsims · Apr 23, 2020 · f814a09 · f814a09
1 parent cdcfcd4
commit f814a09
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/js/accessibility/KeyStateTracker.js b/js/accessibility/KeyStateTracker.js
@@ -310,6 +310,9 @@ class KeyStateTracker {
    */
   attachToBody() {
     assert && assert( !this.attachedToBody, 'KeyStateTracker is already attached to body.' );
+    if ( !document.body ) {
+      throw new Error( 'Cant access body element until it is declared, run script later or in a timeout.' );
+    }
 
     this.bodyKeydownListener = event => {
       if ( this.blockTrustedEvents && event.isTrusted ) {