feat(logout): handle null and undefined on nameQualifier

[sibelius]

microsoft outlook returns

nameQualifier
spNameQualifier

as null instead of undefined

so this PR address this to handle both null and undefined

[markstos]

I manually tested the logic before and after several values: undefined, null, '', 'string', and 0.

I found that the only change in the logic was to treat both "undefined" and "null" the same way, as intended, I'm merging this.

Some automated tests here could be helpful to prevent a related regression in the future.