[BUG] Empty value check

[Kaffiend]

Event for saving configuration should check for empty value before parsing or handle it correctly if it's intentionally empty.
Instead getting an error on the screen when clearing a field, last good value maintained until new valid value.

To Reproduce
Steps to reproduce the behavior:
Server alias field, backspace current value until empty to replace value causes error to show.
Seems harmless currently but can be misleading to users.

Expected behavior
No error or clear message for field if optional

[JensvandeWiel]

This is because it updates the config on every change, even when it is empty