BuildCraft version: buildcraft-all-7.99.21.jar
Forge version: 14.23.5.2807
Link to crash report or log: https://pastebin.com/1r3CsAZM
Singleplayer or multiplayer: multiplayer
Steps to reproduce: It seems to happen after I broke the tank.
Additional information: I checked the server log and saw this error, so I decided to report it.

Oh right it looks like forge's bucket implementation isn't working in quite the way we expected it to - I'll have a look at that in forge.