Replacer crash

[thomasrudin]

Looks like an attempt to replace technic cables
https://github.com/pandorabox-io/technic/blob/pandorabox/technic/machines/register/cables.lua#L246

2019-12-29 13:19:03: ERROR[Main]: ServerError: AsyncErr: ServerThread::run Lua: Runtime error from mod '' in callback item_OnPlace(): ...//worldmods/technic/technic/machines/register/cables.lua:246: attempt to concatenate local 'num' (a nil value)
2019-12-29 13:19:03: ERROR[Main]: stack traceback:
2019-12-29 13:19:03: ERROR[Main]: 	...//worldmods/technic/technic/machines/register/cables.lua:246: in function 'on_place'
2019-12-29 13:19:03: ERROR[Main]: 	/data/world//worldmods/replacer/init.lua:474: in function 'replace_single_node'
2019-12-29 13:19:03: ERROR[Main]: 	/data/world//worldmods/replacer/init.lua:548: in function </data/world//worldmods/replacer/init.lua:508>

[OgelGames]

So it was me... 😄 (I tried to place cable plate with the replacer)

Turns out the crash was partly because of the replacer not passing a proper pointed_thing to on_place(): https://github.com/SwissalpS/replacer/blob/master/init.lua#L473 (above and under positions are the same), but also because there is no nil check or default value assigned to num: https://github.com/pandorabox-io/technic/blob/pandorabox/technic/machines/register/cables.lua#L218

I'm just going to add a nil check to the cables code, but it will mean that the replacer won't work correctly with the technic cable plates (due to the workaround to connected nodes not being rotatable); an additional fix to find a way for the replacer to pass a proper pointed_thing would be needed to make it work correctly.