TYPO3 Core

I tested this with TYPO3 10.4.15

When I'm in the workspace manager module I get occasionally the following error in the console. This happens when I have a new MASK CE which has a repeating field, as far as I can tell.

For that I created a new MASK CE which could have a repeating field. At first a did not create any repeating field inside this MASK CE and got no error in the workspace manager module. The I added a repeating field (a new card) and then I got the error:

Backend.js:13:20244

Uncaught (in promise) TypeError: a is null
renderWorkspaceInfos https://.../typo3/sysext/workspaces/Resources/Public/JavaScript/Backend.js?bust=1618330032:13
loadWorkspaceComponents https://.../typo3/sysext/workspaces/Resources/Public/JavaScript/Backend.js?bust=1618330032:13
loadWorkspaceComponents https://.../typo3/sysext/workspaces/Resources/Public/JavaScript/Backend.js?bust=1618330032:13
Backend https://.../typo3/sysext/workspaces/Resources/Public/JavaScript/Backend.js?bust=1618330032:13
jQuery 11
mightThrow
process
setTimeout handler*resolve/<
fire
add
then
Deferred
then
ready
init
jQuery
Backend https://.../typo3/sysext/workspaces/Resources/Public/JavaScript/Backend.js?bust=1618330032:13
<anonymous> https://.../typo3/sysext/workspaces/Resources/Public/JavaScript/Backend.js?bust=1618330032:13
execCb https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
check https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
enable https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
bind https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
emit https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
each https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
emit https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
check https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
enable https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
bind https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
emit https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
each https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
emit https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
check https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
enable https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
bind https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
emit https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
each https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5
emit https://.../typo3/sysext/core/Resources/Public/JavaScript/Contrib/require.js:5

Not sure if this is a TYPO3 error or MASK issues...