Buildcraft version: Currently the one in use on the dev branch
Forge version: Currently the one in use on the dev branch
Link to crashreport or log (on pastebin or gist, please don't put the entire log here) :
Singleplayer/multiplayer: Singleplayer (multi-untested)

Additional information: Reported on the discord by another user, powering an obsidian pipe with a creative engine causes a null reference when the pipe has no connections, as there is no 'sucking direction'.

I am able to reproduce this reliably and am working on a fix.