I'm sorry to

this thread with a probably n00bish question, but I got to the mission "Circles within Circles" (from STL: Origin). So far, I had in every mission the "Can't open model file <none>" problem, but I could go on anyway.
In this mission, when I get to the weapon loadout screen, I get a slightly different error. It continues popping up, preventing me from starting the mission:
Error: Can't open model file <none>
File:J:\src\cvs\fs2_open_3_6_9.final\code\Model\ModelRead.cpp
Line: 1902
[This filename points to the location of a file on the computer that built this executable]
Call stack:
------------------------------------------------------------------
------------------------------------------------------------------
As you can see, the line is no more 1899 but 1902.
Is there a way to fix this? Thanks!

EDIT: strange... the error doesn't come up anymore...