Removing last condition or action breaks dialogues

[MrGeneration]

Infos:

• Used Zammad version: 3.1
• Installation method (source, package, ..): any
• Operating system: any
• Database + version: any
• Elasticsearch version: any
• Browser + version: Tested and verified on Firefox and Chrome (latest)

This seems to be -at least partly- a regression of #2516

This issue was found by the Community-Member: https://community.zammad.org/u/bebosudo

Expected behavior:

• not being able to remove the last action or condition on modal dialogues.

Actual behavior:

• On most of the dialogues you can remove the last action and/or condition in modal dialogues. This draws the UI useless (if you save that change), because you'll never be able to re-add conditions or actions.

affected interfaces:

This list might be incomplete, but I successfully tested this at least partly (condition or action) on:

• Trigger
• Scheduler
• SLA
• Reporting-Profiles
• Time Accounting
• Overviews
• Postmaster FIlters

Possibly also affects integrations like LDAP, but this is untested.

Screencast with example:

Steps to reproduce the behavior:

• go to any modal dialogue that contains conditions and/or actions
• try to remove all conditions or actions

Yes I'm sure this is a bug and no feature request or a general question.

[bebosudo]

May I suggest a UI improvement?
I think it would be "easier" to use a delete/trash icon on every row of condition/action (as it is now) and a single add with plus icon below.
What's the meaning of having a plus on the first row? Is it any different from the second or third "add" button?