[TYPO3-ttnews] tt_news with categories does not work with Workspaces

[Holger Luechow]

Hi, 
I'm using tt_news v. 3.5.1 with Typo3 4.7.
To implement a workflow I'm using workspaces. 
In the draft workspace the user is able to edit news including the news category. Looks pretty fine at this stage.
But in the list view the category is not stored, though filters in pages cannot deal with categories in this workspace.

A detailled look in the database identified the cause. No entry is made in table tt_news_cat_mm.

In the LIVE workspace everything works fine, tt_news_cat_mm entry is made, list view is ok and filter works.

Has anyone an idea, how to fix this?