make booleanswitcher clean up the targets list while autoaddchildren is enabled

[art0007i]

Is your feature request related to a problem? Please describe.

if you have a booleanswitcher with autoaddchildren, but the children are non-persistent (or the switcher slot has a children save blocker) saving the item and spawning it out will result in null entries which have to be manually removed to return it to the expected state. here's images describing what I mean:

Pics

Before saving:

After saving and spawning out:

Describe the solution you'd like

while autoaddchildren is enabled saving should not create null elements

Describe alternatives you've considered

some jank where i unparent all non-persistent items on saving and put them back in after, it's not a nice solution but the only one I can think of

Additional Context

No response

Requesters

No response

[mpmxyz]

Linking it to AutoAddChildren could break existing content that relies on indices staying consistent across saves.
(i.e. timed slides/animations where parts of the content have been removed but the remainder should stay in place)
There are ways to add items permanently but not keep them within the hierarchy if AutoAddChildren is toggled depending on operation.