"e is undefined" in Panel

I have a table block with the following blueprint layout:

name: Tabelle
icon: menu
preview: table
fields:
	rows:
		type: structure
		label: Zeilen
		fields:
			kuenstler:
				label: Künstler
				type: text
			kuenstler_link:
				label: Link
				type: url
			media:
				type: blocks
				label: Medien
				fieldsets:
					- audio
					video_link:
						name: Video
						icon: video
						fields:
							video_url:
								label: YouTube-/Vimeo-URL
								type: url
							video_title:
								label: Titel
								type: text

If I add a row to the table but leave the media field empty the entire content (table block and all other blocks) are disappearing and instead I’m getting an error “e is undefined” – console says this happens in ~/media/panel/f376cb5a1b86623b83d10dd67acd9ea4/js/app.js

If I add a block in the media field everything is alright; even if I then remove the blocks there afterwards. What am I doing wrong?

Seems you are using tabs, change them to spaces (e.g. 2 spaces per tab).

- audio
video_link:

on the same level? I think this is not valid yaml.

Ah, thanks, my IDE is supposed to know that YAML files should only have spaces; not sure why it used tabs. Anyway, I converted them to spaces but the issue is persisting.

According to Blocks | Kirby CMS it is.

Which Kirby version are you using?

3.5.7.1

And what is saved in the content file for the media blocks field if the field is empty?

I added a table row with the media field empty; it gave me the error but I saved the page anyway and this is printed in the text file:

{"content":{"rows":[{"kuenstler":"Test","kuenstler_link":"","media":""}]},"id":"cd57d20b-c421-4aad-bc30-c49bcbe4e189","isHidden":false,"type":"table"}

After further testing I found that it’s not related to the media field, the error also occurs if any other field is empty. I then removed fields from the blueprint one by one and it seems like the structure field itself is the problem (i. e. if I change the “rows” field to a plain text field there is no error; as soon as it’s changed to a structure and has just one plain text field in it, the error occurs). Could this be a bug in Kirby?

There were some changes in relation to the structure field Vue files, maybe those cause the issue.