Delete icon in toolbar missing

I use 3 tabs - on contains my Gmail IMAP (incoming messages), another is Local Folders (storage area of messages) and third is my newsgroup. When I go to newsgroup-tab toolbar icon for deleting messages disappear and that is of course correct. But when I come back to gmail or local folders tab delet icon doesn't come back. It happens most likely at first time going to newsgroup tab and switching back. If I stays default folder (gmail inbox) delete icon is away but when I switch to another gmail folder delete icon appears again.
I can also (in my newsgroup tab) switch to another news-account and then delete icon disappears as expected. After that when I go to gmail tab toolbar is the same and delete icon is missing.

So it seems that switching tab doesn't trigger refreshing toolbar in all cases.