SPIGOT-1546: Use isPassenger, not misleading getVehicle

CraftBukkit-Patches/0014-Entity-Activation-Range.patch

@@ -427,7 +427,7 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +        }
 +        if ( !( entity instanceof EntityArrow ) )
 +        {
-+            if ( !entity.onGround || !entity.passengers.isEmpty() || entity.getVehicle()!= null )
++            if ( !entity.onGround || !entity.passengers.isEmpty() || entity.isPassenger() )
 +            {
 +                return true;
 +            }