[rt-users] Unassigning tickets does not work

[JC Boggio]

Since we upgraded from RT 3.8 to 4.0.4, we can't assign tickets to Nobody anymore.
To anybody else works.

When I give to someuser history says :
"JC Boggio - Given to someuser"

When I try to give to nobody, I get :
"JC Boggio - Not taken"

(These are free translations from french)

Any clues ?

Thanks,

JC