Add-ons server keeps undefined properties at their previous value upon update

[vgaming]

Game and System Information

• What version of the game are you running? wesnoth_addon_manager version 170ec9b 2021-09-25
• Where did you download it from? git clone
• What OS are you running? ArchLinux

Describe the bug

Context: I have an add-on (Creep_Wars_Dev) that I try to update. It previously had a dependency on pick_advance, and now I want to remove it as it's a built-in wesnoth dependency now.

The bug happens when I update the add-on using wesnoth_addon_manager. I'm using this _server.pbl: https://github.com/vgaming/CreepWars/blob/8a417ccf1ec12e589079845674490165d7ff82f3/Creep_War_Dev/_server.pbl which has no dependencies defined.
When I update my addon, the add-on store says that my addon is accepted. The version is updated accordingly, as seen in the game client. However, the dependency does not get removed and remains to be the old one.

In other words, updating an addon with not-specified dependencies did not cause removal of the dependencies. The only thing that worked was to submit this update: vgaming/CreepWars@1d2358c after which everything worked as expected

Steps To Reproduce

1. Create a new add-on with a dependency specified
2. Use wesnoth_addon_manager to publish the addon
3. Remove the dependency from the add-on
4. Update the addon
5. Observe from the game client that the add-on still requires the old dependency

Expected behavior

After publishing an add-on that does not specify any dependencies, dependencies should be removed by the addons server

Screenshots

[soliton-]

Official add-on server instances have been restarted with the fix.