Classification should always be set via `ndpi_set_detected_protocol()` to be sure to set a correct `confidence` value, too. Having a "known" protocol stack with `NDPI_CONFIDENCE_UNKNOWN` as confidence, is not valid. This code in HTTP dissector likely needs some more thoughts (the classification itself of the attached example doesn't make a lot of sense), but the goal of this commit is only to always have a valid `confidence` value.