a stacktrace prints out each time an electric vehicle is placed down, was tested using "electric locomotive" from this mod:
https://mods.factorio.com/mod/Realistic_Electric_Trains

3225.095 Script @Fill4Me/stdlib/event/event.lua:153: Unknown item name: seedling
stack traceback:
Fill4Me/fill4me/fill4me.lua:193: in function 'getFromInventory'
Fill4Me/fill4me/fill4me.lua:265: in function 'load_fuel'
Fill4Me/fill4me/fill4me.lua:114: in function <Fill4Me/fill4me/fill4me.lua:106>
[C]: in function 'pcall'
Fill4Me/stdlib/event/event.lua:148: in function <Fill4Me/stdlib/event/event.lua:127>

Any chance that this might be something different? I was unable to reproduce the error you described, but I think it might be related to another recent change. Any chance you had disabled a mod you previously had enabled in this save?

I'd recently made a change to have fuel selection be per-player, but I think I might have missed a condition, so this might be a mistake from that particular change. I will look into fixing up the recent change and fix this for you.

yes.. seedling was probably from bob's greenhouse - was previously in that save and counts as a fuel type.

As a workaround, try using /f4m.exclude seedling for your current game, until I have time to get this resolved in a clean manner.

the command gave the message "not found in active list"?

I did find a workaround though, disable fill4me, save the game, re-enable fill4me.

I suppose that would work too.