Fix position in some plugin-called player_interact events

This was noticed with Axiom calling RIGHT_CLICK_BLOCK events without a position, but may happen with other plugins too.

Author: PseudoKnight

src/main/java/com/laytonsmith/abstraction/bukkit/events/BukkitPlayerEvents.java

@@ -604,7 +604,7 @@ public MCEquipmentSlot getHand() {
 		public Vector3D getClickedPosition() {
 			Vector v = pie.getClickedPosition();
 			if(v == null) {
-				return null;
+				return Vector3D.ZERO;
 			}
 			return new Vector3D(v.getX(), v.getY(), v.getZ());
 		}