TB 45 Treechildren (Message List) always folded

[Acid Crash]

Hi to everyone.
After updating to TB45 I discovered that TB started to ignore Treechildren (Message List) state.
I use Group by date -> Grouped By Sort method setting.
In 38.5 all of my groups were collapsed (manually collapsed them) and remained this way after restart of the app.
In TB45 after restart all of my groups are folded again.
Is there a way to fix this or make groups collapsed by default (a dirty fix via userchrome.css or stylish will work for me too)

[alta88]

See this: https://bugzilla.mozilla.org/show_bug.cgi?id=1265176