This problem appeared after Leap RC1 (first spotted this in build 0258) and in
TW 20151022. 

I have to keep Dolphin windows and tabs from one session to another but this
appears to be no longer possible. When I log out, I get a window pop up warning
me that I have tabs open and giving me three options, "quit", "close current
tab", or "cancel". None of these appear to help me achieve my desire. 

The really marvellous one to try is "cancel"! That not only cancels the closing
of any Dolphin tabs but cancels the logout process. That wouldn't be so bad if
it didn't also freeze the screen making the Vulcan neck-pinch (ctrl+alt+del)
the only way of escaping. In the end, it achieves the same result as the others
in that at the next logon, Dolphin is not restarted automatically and, when
started by hand, all tabs and windows are lost.

This change would be annoying at any time but for it to appear days before a
major new release of Leap seems bizarre.