Can you please provide a crash report or a relevant log of when the crash happens? Also, what version of SecurityCraft are you using?

Thank you for reporting this! While it was an easy problem to reproduce, please always under any circumstances when reporting crashes include the Minecraft version, the mod version, and any logs (latest.log, debug.log, and most importantly the crash report as well). This helps mod authors to diagnose issues more quickly.

the logs! https://mclo.gs/HcbOk7I

Thank you, but I already fixed it. A new version will be released shortly!