Rotating the mouse wheel over a dead number input changes the number even though it is a corpse. ???
People don't expect that dead guy to count.
The workaround I came up with is no action when number_input is dead.
https://github.com/Ranran-the-JuicyPork/simutrans-exp/commit/297bc31677ce2da8c839b8bf5b06ec42def8477b
Included in r10797, thanks