Error when using nickname field in search

Hi all,
I have a few charts on my “RT at a glance” page, to summarize our ticketing activity.
Today I edited the charts and changed the “group by” option from “name” to “nickname”.
The charts still display correctly. However, before I was able to click on a row in the associated data table and see the results page.

Now when I click on a row in the associated data table I get an error saying:

There was an error parsing your search query: Invalid watcher subfield: ‘NickName’. Your RT admin can find more information in the error logs.

In the log I can see this:

Stack:

[/opt/rt4/sbin/…/lib/RT/Tickets.pm:1025]

[/opt/rt4/sbin/…/lib/RT/Tickets.pm:3029]

[/opt/rt4/sbin/…/lib/RT/SQL.pm:172]

[/opt/rt4/sbin/…/lib/RT/Tickets.pm:3037]

[/opt/rt4/sbin/…/lib/RT/Tickets.pm:3055]

[/opt/rt4/share/html/Search/Results.html:120]

[/opt/rt4/sbin/…/lib/RT/Interface/Web.pm:681]

[/opt/rt4/sbin/…/lib/RT/Interface/Web.pm:369]

[/opt/rt4/share/html/autohandler:53] (/opt/rt4/sbin/…/lib/RT/Tickets.pm:3059)

[23990] [Fri Oct 30 09:23:01 2015] [error]: Couldn’t parse query: Invalid watcher subfield: ‘NickName’ at /opt/rt4/sbin/…/lib/RT/Tickets.pm line 1025.

Is this nromal behavior?
I can see how using nicknames should not be a very important feature in RT, however I believe RT should at least handle it more gracefully.

Cris