tora crashes on closing tab

[Rolf Leggewie]

I have the following reproducible crash with tora 2.1.3-2build2 on trusty.

- open tora and connect to DB (I used a MariaDB on the LAN)
- Choose Tools - Schema Browser from the menu
- Close the tab that was just opened

The program will hang briefly and then crash with the following backtrace on the console.

$ tora
[...]
tora: /build/buildd/tora-2.1.3/src/tomain.cpp:1723: void toMain::workspaceCloseWindow(int): Assertion `w' failed.
Aborted (core dumped)