Steps to reproduce
Camunda 7.12.3 Wildlfy distro. Also reproducible in Tomcat distro.

1. Log into Tasklist application
2. Select any user task with generated form / embedded form
3. Log out from the Tasklist application.

Now, following error message appears in the browser's console (Chrome).

 TypeError: Cannot read property 'target' of undefined
    at camunda-tasklist-ui.js?bust=7.12.3:7
    at deps.js?bust=7.12.3:1
    at ri.completeTask (deps.js?bust=7.12.3:1)
    at deps.js?bust=7.12.3:1

Expected: There should not be any error in the console.