Code:
[12:44:38] [Server thread/WARN]: Unknown target reason, please report on the issue tracker
java.lang.Exception: null
at net.minecraft.server.v1_12_R1.EntityInsentient.setGoalTarget(EntityInsentient.java:138) [spigot.jar:git-Spigot-7754231-362ed32]
at net.minecraft.server.v1_12_R1.EntityInsentient.setGoalTarget(EntityInsentient.java:128) [spigot.jar:git-Spigot-7754231-362ed32]
at...