Christ never said the Catholic Church or Pope would never be in error. Nor would I believe for a second that they never have been in error before.
whatsoever you shall bind on earth shall be bound in heaven, whatsoever you shall loose on earth shall be loosed in heaven.......do you think that He would allow the Catholic Church to bind something in error that He would also have to bind in heaven????
if you can find an error that any Pope has ever made in official church teachings (not behavior) then you would be the first person in history to do so......millions have tried!!