Highlight button for currently selected details panel section in task list

Description of problem:
Please implement the simple enhancement to let user know which section of task details is currently selected. See screenshots.

Currently it is not immediately clear which section of task details (Work/Assignments/Details/Comments) is currently selected.

You could use the existing 'active' class to make it more obvious which one is selected. As a bonus it would also improve UI testability

Version-Release number of selected component (if applicable):
BPMS 6.0.0 ER4

How reproducible:
Always

Steps to Reproduce:
1. Go to Tasks > Task list
2. create a new task and go to details panel by clicking the magnifying glass
3. notice,

Actual results:
The buttons at the top of the details panel (Work/Assignments/Details/Comments) are not highlighted, it's not clear which section user has currently selected - he has to inspect the contents of the panel to find out.

Expected results:
One button should be highlighted to make it clear which section is currently selected.

Additional info: