I would only support this if it applied only to debates that received zero votes. Maybe a debate was actually just that even. Maybe they just had such a close debate that the tie is warranted. In any case, I don't think this should matter, and such debates should end in a tie.
In debates, there is almost always someone who emerges victorious; someone who has the skill and the willpower to persuade people into taking a certain position. So, having debates ending in zero votes and ties should definitely be allowed extensions to the voting period. This helps newcomers to the site (such as myself) as well as frequent users be able to get clear results and constructive criticism on debates to further enhance their intellectual capability and build upon their logic and reasoning skills, as well as help put in the art of persuasion and encourage debate in general.