Changes

correction to the previous commit

please --squash this or the previous ones.
(and i'll try not to write up commits using the web interface, even for
simple things in the future)
 (commit: a48e184)

another null check needed

the crafting helper is not used anywhere other than the 3 places that
have null checks. (this was the third location)
 (commit: 131f245)

fix transport pipe explosions not destroying the pipe
 (commit: 81db6ee)