[lmi] [PATCH] Avoid crashes if the GUI test is aborted

[Vadim Zeitlin]

 Hello,

 I believe you've already seen this as well, when the tests ran into some
problem and crashed on exit, after executing prematurely and spewing a lot
of gibberish on the console, but I've just run into this myself by
accidentally switching to the running test window and closing it and, after
realizing that this was enough to reproduce the crash, I could easily debug
and fix it.

 The problem is that the test code tries to close the main window on exit,
but if the main window had already been closed, for whatever reason, the
pointer to it is invalid any longer. The patch at
https://github.com/vadz/lmi/pull/24/files fixes this by closing the current
top window if it still exists and is enough to avoid crashing if the test
is interrupted (but not the simulated input appearing on the process
controlling terminal...).

 As usual, please let me know if you have any questions about this patch
and thanks in advance for applying it,
VZ