Tabular View Fixes

[Amantini1997]

Description

A list of small features and bug fixes for tabular view #4347

• Remove "Unset" group when default exists. Some grouping options have the "Unset" group batch at the bottom. This should only be displayed if the template does not have a default value for the respective property. e.g. The user groups by priority. If the property in the template come with a default value (default), then the group batch "Unset" should not exist as it is "unreachable".
• Assignees are not sorted correctly. Some empty values are sorted to the top and some are sorted to the bottom
  • Assignees should be sorted by number of assignees, then alphabetically