The assertion is only triggered when the opponents race track is destroyed, one can also trigger it from within the editor by loading the map and deleting the race track.

The problem lies within the tutorial data itself, Map::load loads a map description into map->cases where the race track occupies an area of size 6x6.

The building however is of type 15 (racetrack0c, racetrack level 0 in construction). The size of the racetrack level 0 is 4x4. When the building is destroyed, map->cases has to be updated. But since the building is actually smaller than the 6x6 area that is marked as occupied on the map, a 2 unit wide border is left referencing the building.

When a map to building look up is performed on that shadow, the
assertion is triggered.

I fixed the map by setting the buildings type to 17 (racetrack1c,
racetrack level 1 in construction). You can find the corrected map for 0.9.4 at

http://cache.jade-hamburg.de/~teythoon/stuff/tutorial-part4.map

This bug is also being tracked at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=595448

Cheers,
Justus

I've the same bug in GNU/Linux, with this line :

glob2: src/Building.cpp:2848: void Building::integrity(): Assertion `(*it)->targetBuilding==this' failed.