[Merkaartor] Crash when closing a layer

[Yves Goergen]

I just closed a map layer in Merkaartor and then it crashed. Before
that, I have first downloaded one region and then another reagion nearby
(with "Download", not "Download more"). Then I tried to close the layer
of the first download. No other actions taken.

Unfortunately something reverted my build to non-debug so I cannot
provide any stacktrace information for now. I have now switched to debug
(again) and will re-test.

Latest SVN build.

-- 
Yves Goergen "LonelyPixel" <nospam.list at unclassified.de>
Visit my web laboratory at http://beta.unclassified.de