Ship freezes loaded with wares upon destruction of destination port

This is a bug report at Nasenbaer's request.

I had three ports, call them A, B and C. The ships were transporting all the wares between A and B however I wanted the ships to deliever the wares to C. Therefore I destroyed port B, however in doing so one of the loaded ships lost its destination and simply froze up without ever delivering the wares. The other remaining ships continued to deliver goods between A and C.

Just to be clear, at the moment of the port removal I had three functioning ports, when I deleted one I had two left.