Off the top of my head, here are two possibilities to check:
1. Respondent terminated the questionnaire early, prior to getting to the respondent's last Choice tournament question.
2. Respondent indicated that not enough of the Screener concepts were a possibility, so no Choice Tournament question (involving 3 concepts at a time) were possible to be shown. For example, if only one or two concepts were selected as a "possibility" in the Screener section and the Choice Tournament was set to show triples ( 3 at a time), then it wouldn't be possible to show a question in the Choice Tournament section and thus no Tournament winner exists.