Context

Imagine the follow scenario:

1. You upload a dataset 'A' and create an annotation.
2. Later, you delete 'A'. The annotations remains in WK, however.
3. You open the annotation, but WK crashes.

Example annotation:
https://webknossos.org/annotations/68ca6d8c0100000801c600e6

Expected Behavior

There should be a meaningful error message. WK should not crash.

Current Behavior

WK crashes with:
Initialization error. Please refresh the page to retry. If the error persists, please contact an administrator. TypeError: Cannot read properties of undefined (reading 'slice')

Steps to Reproduce the bug

See above

Your Environment for bug

• Browser name and version: all
• Operating System and version: all
• Version of WEBKNOSSOS (Release or Commit): 17913035221
• Specific to long-running jobs (set jobsEnabled=true in application.conf)
• Specific to webknossos.org (set isDemoInstance=true in application.conf)