maintain previous behavior

selfdrive/car/car_helpers.py

@@ -67,6 +67,7 @@ def can_fingerprint(logcan: SimpleNamespace) -> tuple[str | None, dict[int, dict
           if can.src == b and can.address < 0x800 and can.address not in (0x7df, 0x7e0, 0x7e8):
             candidate_cars[b] = eliminate_incompatible_cars(can, candidate_cars[b])
 
+      if len(can_packet) > 0:
         # if we only have one car choice and the time since we got our first
         # message has elapsed, exit
         for b in candidate_cars: