@initiator doesn't work for players that are enabled with dialogue command

@initiator doesn't work for players that are enabled with dialogue command.

Steps:

1. creat a npc name A (tag=A) -P1

2. creat another npc name B (tag=B) -P2

3. creat a button(open B) command(/dialogue open @e[type=npc,tag=B] @initiator)

to npc A  -P3

4. creat a button command to npc B.Command:/give @initiator diamond 

5. click the button(open B) -P4

6. the screen will turn to npc B -P5

7.click the button(sword)

Observed:

Step1~step6 in  great

Step7,you cant get diamond after clicking the button(diamond),if you change @initiator into @p it can work ,but @p is not i want

expected results:

you can get the diamond after clicking the button.I am doing that way is because npc can only creat up to 6 buttons,the only way is creat a button into the button like what i do.