See https://mods.factorio.com/mod/SpidertronPatrols

When clicking on a Vehicle Dock while a vehicle is docked (e.g. a spidertron):

The mod Filter Helper (0.2.12) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event FilterHelper::on_gui_opened (ID 98)
LuaInventory API call when LuaInventory was invalid.
stack traceback:
[C]: in function 'index'
__FilterHelper/filter_updaters.lua:19: in function 'condition'
FilterHelper/filter_updaters.lua:286: in function 'get_filter_updater'
FilterHelper/control.lua:496: in function 'update_ui'
FilterHelper/control.lua:555: in function <FilterHelper/control.lua:550>

maybe https://github.com/MESLewis/FilterHelper/pull/18

at least when I apply those changes in the mod's zip, the error isn't raised - however, I have no clue at all whether this leads to unintended sideeffects or subsequent errors. I'll play a while with these changes and see where it leads me, until it's "officially" fixed...

This fix should not be needed, as the holding entities are checked for validity just before it.

I'll give it a longer look.

OK this seems to be related to the new proxy-containers. I'll produce a fix soon enough.

Should be working now

Yes! nice work (thumbsup)