CoreLib Issue with RankPrefixPlus

[16:26:35 INFO]: [CS-CoreLib - Updater] RankPrefixPlus is up to date!
[16:26:35 WARN]: Exception in thread "Thread-19"
[16:26:35 WARN]: java.lang.ArrayIndexOutOfBoundsException: -1
[16:26:35 WARN]:        at java.util.ArrayList.elementData(Unknown Source)
[16:26:35 WARN]:        at java.util.ArrayList.get(Unknown Source)
[16:26:35 WARN]:        at me.mrCookieSlime.CSCoreLibPlugin.updater.Updater$Upda
terTask.connect(Updater.java:70)
[16:26:35 WARN]:        at me.mrCookieSlime.CSCoreLibPlugin.updater.Updater$Upda
terTask.run(Updater.java:58)
[16:26:35 WARN]:        at java.lang.Thread.run(Unknown Source)