Exception in server tick loopjava.lang.NoSuchFieldError: openTabs

[Former user]

I am currently running a modded minecraft 1.6.4 server with a variety of different mods. I was trying to create a High Pressure Tank after successfully creating one on my single player test world, and whenever I place the controller block down for the tank, i get this nasty crash report: https://pastebin.com/aC01qwds

I know this is an older version of minecraft, but if you happened to have time to take a look at it and possibly create a solution, i would be very appreciative. Thank you for whatever you can/have time to do!

[Patrick Ziegler]

Hi, I have stopped working on HPTanks some time ago. Since this is additionally a really old version of the mod, I will not publish an update because it would take a lot of time, I don't have. I'm sorry, but I suggest you migrate to a newer version.