Deleting a movement order instead duplicates it

[ekolis]

Describe the bug
Deleting a movement order from a fleet causes it to be duplicated at the end of the queue instead.

Steps to reproduce

1. Select a fleet (not sure if this works with individual ships).
2. Give it some orders.
3. Delete one of the orders (from the fleet's orders tab).

Expected behavior
The order is deleted.

Actual behavior
The order is copied to the end of the queue.

Screenshots
N/A

Related issues
N/A

Testing plan
???

Additional context
N/A