How to flush assignee with jira 6.4.13

[desire]

Hello,

I was previously using Jira 5.2.11 and use the following code to flush the assignee in my jira plugin.

issueInputParameters.setAssigneeId(null);

But, when we migrated to jira 6.4.13, the same code doesn't work again.

Can you please help?

It seems that this method is not deprecated.

[Nic Brough _Adaptavist_]

Could you explain what " flush the assignee " means?