There is no need to enter your middle name at all. That is the most simple solution.
I've seen occasional cases (rare) where middle name issues do cause problems, but never once heard of anyone having a problem with it entirely omitted. Even in the US where TSA claims that you have to match your passport name, I only ever use my middle name when United.com issues the ticket. If I do it on Expedia, etc., I leave it off and TSA couldn't give a care.
Overseas, absolutely no issues with leaving it omitted.