Traffic: adjust failure of for reachedEndOfCruise

When reachedEndOfCruise fails, return true, so we trigger the next
phase of the flight. Without this we get stuck logging the error
message, but not progressing the flight.

src/AIModel/AIAircraft.cxx

@@ -1341,7 +1341,9 @@ bool FGAIAircraft::reachedEndOfCruise(double &distance) {
     FGAIWaypoint* curr = fp->getCurrentWaypoint();
     if (!curr) {
         SG_LOG(SG_AI, SG_WARN, "FGAIAircraft::reachedEndOfCruise: no current waypoint");
-        return false;
+
+        // return true (=done) here, so we don't just get stuck on this forever
+        return true;
     }
     
     if (curr->getName() == string("BOD")) {