e.g. r6197: crash after reloading after copying trains

[whoami]

Symptom: upon reloading certain savegames from r6197 and some earlier ones (Win-SDL), ST exits with the message "FATAL ERROR: depot_t::vehikel_laden() - invalid vehicle type ¢22D24C" (yes, that is a credit/cent symbol). The savegame is therefore unusable.
This bug has cost me a lot of time (first losing my savegames three times, then tracking it down).

How to reproduce (exactly):
- load this savegame with pak64+food (V112): http://simutrans-germany.com/files/upload/Wernieman_STIF20120722_X198_M79c_r6197_SJ1984_disasm.sve (Wernieman had created and developed this game, then I took it over.) (Note: this one is large, 6.5 MB compressed.)
- (optional?) pause
- open the train depot at (172,882) (the one at Neuss BF+FH)
- assemble a train (length 7) with "BR103" and 13 "H-Trans Passenger Car"s (the one that has 98 stored there)
- assign line "Bahn 01 Z7F Neuss-...-Kass" to this train
- copy this train nine times (to get 10 of them)
- close depot
- save game
- (optional: restart Simutrans)
- reload this savegame
- watch the fatal error

Note: in the same depot, several shorter trains (the ones with "Class 86") from the same line had been gathered and disassembled. If there are already errors in the savegame provided by me, I can provide earlier states.

[Dwachs]

Very strange thing. When cloning the trains, suddenly the orange locomotives vanish, the depot window shows '56 vehicles' but apparently no vehicles are there...

Edit: r6206 should fix this.