if you destroy stormwall emitters that cover the same wall at the same time the game crashes

the error notice:
Error while running event Stormwall::on_nth_tick(20)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
[C]: in function' _ _ index' _ _ Stormwall _ _ /control.lua:699: in function
< _ _ Stormwall _ _ /control.lua:685>

i would love to see it fixed

edit: actually, after some more testing, it seems to appliy to "built" walls too

Should be fixed in 1.4.2.

thanks for the fix