Seen this a few times in the console now. If I can suss out what triggers it I will report back.
[14:22:54 WARN]: [Citizens] Task #3442715 for Citizens v2.0.41-SNAPSHOT (build 4059) generated an exception java.lang.NullPointerException: Cannot invoke "org.bukkit.entity.Entity.getType()" because the return value of "net.citizensnpcs.api.npc.NPC.getEntity()" is null at Citizens-2.0.41-b4059.jar/net.citizensnpcs.trait.waypoint.triggers.AnimationTrigger.onWaypointReached(AnimationTrigger.java:39) ~[Citizens-2.0.41-b4059.jar:?] at Citizens-2.0.41-b4059.jar/net.citizensnpcs.trait.waypoint.Waypoint.runTriggers(Waypoint.java:107) ~[Citizens-2.0.41-b4059.jar:?] at Citizens-2.0.41-b4059.jar/net.citizensnpcs.trait.waypoint.Waypoint.lambda$runTriggers$0(Waypoint.java:116) ~[Citizens-2.0.41-b4059.jar:?] at org.bukkit.craftbukkit.scheduler.CraftTask.run(CraftTask.java:78) ~[paper-1.21.8.jar:1.21.8-56-65641d1] at org.bukkit.craftbukkit.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:474) ~[paper-1.21.8.jar:1.21.8-56-65641d1] at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1663) ~[paper-1.21.8.jar:1.21.8-56-65641d1] at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1531) ~[paper-1.21.8.jar:1.21.8-56-65641d1] at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1253) ~[paper-1.21.8.jar:1.21.8-56-65641d1] at net.minecraft.server.MinecraftServer.lambda$spin$2(MinecraftServer.java:310) ~[paper-1.21.8.jar:1.21.8-56-65641d1] at java.base/java.lang.Thread.run(Thread.java:1583) ~[?:?]