Calls directly MovementSolver::traceDown instead of

PhysicsSystem::traceDown before inserting into mActors.

The latter does nothing until the actor is inserted into mActors.
We can't move the call after the insertion either because then
the actor is part of the simulation, and we'd have a race.

apps/openmw/mwphysics/physicssystem.cpp

@@ -725,8 +725,7 @@ namespace MWPhysics
         auto actor = std::make_shared<Actor>(ptr, shape, mTaskScheduler.get(), canWaterWalk);
         
         // check if Actor is on the ground or in the air
-        traceDown(ptr, ptr.getRefData().getPosition().asVec3(), 10.f);
-
+        MovementSolver::traceDown(ptr, ptr.getRefData().getPosition().asVec3(), actor.get(), mCollisionWorld.get(), 10);
         mActors.emplace(ptr, std::move(actor));
     }