We all have done it, and we all have strategies for not dropping cake batters down the center tube of an angel food or bundt pan. A solution that has worked for us is to "cap" the center tube's opening. We have tried 3 different ways.
Our favorite, as pictured, is to "cap" the opening with a small piece of plastic wrap and wrap it around the center tube about a half inch down the tube to hold it in place.
A small circle of aluminum foil folded over the center tube or a bottle cap that sits snugly on top work too. Both of these may dislodge.
Remember to remove your "cap" before popping your cake into the oven.