Fix NPE on null loc for EntityTeleportEvent

EntityTeleportEvent#setTo is marked as nullable and so is the
getTo method. This fixes the handling of a null "to" location
by treating it the same as the event being cancelled. This is
already existing behavior for the EntityPortalEvent (which
extends EntityTeleportEvent).

paper-server/patches/sources/net/minecraft/world/entity/TamableAnimal.java.patch

@@ -74,7 +74,7 @@
 -            this.moveTo((double) x + 0.5D, (double) y, (double) z + 0.5D, this.getYRot(), this.getXRot());
 +            // CraftBukkit start
 +            EntityTeleportEvent event = CraftEventFactory.callEntityTeleportEvent(this, (double) x + 0.5D, (double) y, (double) z + 0.5D);
-+            if (event.isCancelled()) {
++            if (event.isCancelled() || event.getTo() == null) { // Paper - prevent NP on null event to location
 +                return false;
 +            }
 +            Location to = event.getTo();