Bug on remove vertex

[lvca]

I have 3 vertices N1, P1, N2:

• N1 is connected with P1 with two edges.
• P1 is connected with N2 with two edges.

N1 ----> P1 ----> N2
+--------^

create vertex V set name = 'N1'                           
create vertex V set name = 'P1'
create vertex V set name = 'N2'
select from V where name in ['N1', 'N2', 'P1'];

----+----+----
0   |#9:0|N1  
1   |#9:1|P1  
2   |#9:2|N2  
----+----+----

create edge E from #9:0 to #9:1 set name = 'e1';          
create edge E from #9:0 to #9:1 set name = 'e2';
create edge E from #9:1 to #9:2 set name = 'e3';

select from V where name in ['N1', 'N2', 'P1']; 

----+----+----+-----+-----
0   |#9:0|N1  |[2]  |null 
1   |#9:1|P1  |#10:2|[2]  
2   |#9:2|N2  |null |#10:2
----+----+----+-----+-----

Well now I remove the vertex P1.

delete vertex #9:1
select from V where name in ['N1', 'N2', 'P1'];

----+----+----+----
0   |#9:0|N1  |[2] 
1   |#9:2|N2  |null
----+----+----+----

References in N2 have been removed (value = null) but for N1 I still have two references if the result of the previous select is valid. I expected a null value also but the result is [2]. But when I do the following select the result is empty.

select expand(out_) from V where name in ['N1', 'N2', 'P1'];

So that sounds like a bug.