java.lang.NullPointerException: Exception in server tick loop
at mca.packets.PacketInteract.processOnGameThread(PacketInteract.java:305)
at radixcore.network.AbstractPacketHandler.processPackets(AbstractPacketHandler.java:158)
at mca.core.forge.EventHooksFML.serverTickEventHandler(EventHooksFML.java:151)

I have the same problem, is there a fix? I did not understand how to decompile the file to make the change in WildBamaBoy's post.