Items table crafting fixing

* Fixes #4820 

For recipes containing _/obj/items_ (meteorshell and pulseshell are, currently, the only recipes containing these), the problem was that, when looking for _n_ items of the same type in the table content, it located _n_ times the same one.

When a corresponding item is found in the table content, it's location is now set to _null_ to prevent that (the item is eventually relocated into the newly craft item further in the code).

_Note that meteorshell is supposed to requires two manipulators, as pulseshell is supposed to requires two advanced capacitors._

* Small typo in construction fixed