Fix wrong numbers (and crash) in charts when query uses QueueCF

[elacour]

RegisterCustomFieldJoin is tied to RT::Tickets, not RT::Report::Tickets

error: Couldn't parse query: We don't know how to join for LookupType RT::Queue at /srv/rt/rt/sbin/../lib/RT/SearchBuilder.pm line 366.

Stack: [/srv/rt/rt/sbin/../lib/RT/SearchBuilder.pm:366] [/srv/rt/rt/sbin/../lib/RT/SearchBuilder.pm:687] [/srv/rt/rt/sbin/../lib/RT/Tickets.pm:1236] [/srv/rt/rt/sbin/../lib/RT/Tickets.pm:3131] [/usr/share/perl5/vendor_perl/Tree/Simple.pm:441] [/srv/rt/rt/sbin/../lib/RT/Tickets.pm:3141] [/srv/rt/rt/sbin/../lib/RT/Tickets.pm:3159] [/srv/rt/rt/sbin/../lib/RT/Report/Tickets.pm:470] [/srv/rt/rt/share/html/Search/Elements/Chart:59] [/srv/rt/rt/share/html/Search/Chart.html:129] [/srv/rt/rt/sbin/../lib/RT/Interface/Web.pm:696] [/srv/rt/rt/sbin/../lib/RT/Interface/Web.pm:375] [/srv/rt/rt/share/html/autohandler:53]

[netsandbox]

@elacour There is already PR #181 regarding this.