Empty Shared Roster Group options might confuse ejabberd 2.1.10

Hey folks,

we're having troubles with ejabberd-2.1.10 after upgrading from 2.1.8.

We backupped the data and loaded it into the new 2.1.10 server.

We have many shared roster groups which worked well with 2.1.8.

Now, ejabberd complains with the following stacktrace and people don't get the full shared roster groups, but only groups with a limited number of people in them.

The stacktrace is the following:

=ERROR REPORT==== 2012-01-30 22:27:13 ===
E(<0.347.0>:ejabberd_hooks:335) : {{case_clause,[]},
                                   [{mod_shared_roster,split_grouphost,2,
                                     [{file,"mod_shared_roster.erl"},
                                      {line,1122}]},
                                    {mod_shared_roster,is_group_enabled,2,
                                     [{file,"mod_shared_roster.erl"},
                                      {line,467}]},
                                    {mod_shared_roster,
                                     '-get_user_displayed_groups/1-lc$^0/1-0-',
                                     2,
                                     [{file,"mod_shared_roster.erl"},
                                      {line,607}]},
                                    {mod_shared_roster,get_user_roster,2,
                                     [{file,"mod_shared_roster.erl"},
                                      {line,137}]},
                                    {ejabberd_hooks,run_fold1,4,
                                     [{file,"ejabberd_hooks.erl"},{line,331}]},
                                    {mod_roster,process_iq_get,3,
                                     [{file,"mod_roster.erl"},{line,223}]},
                                    {gen_iq_handler,process_iq,6,
                                     [{file,"gen_iq_handler.erl"},{line,116}]},
                                    {gen_iq_handler,handle_info,2,
                                     [{file,"gen_iq_handler.erl"},
                                      {line,177}]}]}
running hook: {roster_get,[{"user","host.de"}]}

If you tell me how to obtain more information to debug this issue, I'll gladly provide it.

Is there any quick remedy?

Our shared roster groups can have the empty list as group options. We believe that this confuses get_user_displayed_groups to return an empty group and hence the string:tokens doesn't return anything useful for the case around it. We are however unsure what the code in the traceback is doing exactly.

Thanks in advance