Angular Error: NgClass can only toggle CSS classes expressed as strings

[KarolDabrowski]

Reduced Test Case

https://stackblitz.com/edit/github-eiwdny?file=src/app/app.component.html

Do you understand that if a reduced test case is not provided, we will intentionally delay triaging of your ticket?

• I understand

Which connector are you using (React/Angular/etc)?

Angular

Bug Description

I'm using premium plugin resource-timegrid at version 6.1.1 with angular wrapper. I wanted to customize labels of resource columns with custom angular content templates:

<full-calendar #calendar
                 [options]='calendarOptions'>
   <ng-template #resourceLabelContent let-arg>
      Whatever
   </ng-template>
</full-calendar>

But mysterious error keep showing up in the console:
Error: NgClass can only toggle CSS classes expressed as strings, got undefined and lots of uncomprehensible stack traces after. On local serving it somehow works, but on stackblitz it even causes resource labels to not show at all. In both cases, it stains console in red and thats quite nasty.
Is this a bug, or maybe I understood something wrong in usage?😅

[KarolDabrowski]

Small update, looking further into, local serving only shows the first custom resource label, but the rest does not show at all after the error.

[iCrawl]

Just to chip in, same thing happens with the #dayHeaderContent injection

[arshaw]

queued for release fullcalendar/fullcalendar-workspace@e27502c

[arshaw]

Released in v6.1.3

Updated repro:
https://stackblitz.com/edit/github-eiwdny-saizsv?file=src%2Fapp%2Fapp.component.html