Fix editor dock layout not saving correctly

[MinusKube]

Fixes #57142

When saving the editor dock layout, the dock_[...] keys were never erased when names was empty, causing the config to keep the old values for these keys.

For example, if you had:

dock_1="Node"
dock_2="Inspector"

And you moved Node to dock_2, this was the result:

dock_1="Node"
dock_2="Inspector,Node"

It now makes sure the key is erased if names is empty (it also erases it even if it's non-empty, so the keys are always ordered correctly in the config).

This issue was caused by a regression from #48466

[akien-mga]

Thanks!