Switching inventories while traiding (crashdump 0.75.3)

[ScarabParamit]

Some things have changed...i was unable to switch party inventory while traiding (like in 0.74...) to quickly sell all i wanted - trade window just closes. So i tried with "locking" inventory window of interacting member thinking this would prevent his and traiders inventory from closing ...but in result it lead to gamecrash ^^'

Crashdump uploaded.

Regards.