The fix introduced in a02fc2cd (2011-05-24; index: correctly parse
invalidated TREE extensions) threw out the rest of the data in the
extension if it found an invalidated entry. This was the result of
incorrect reading of the documentation.

Insted, keep reading the extension, as there may be cached data we can
use.

Signed-off-by: Carlos Martín Nieto <cmn@elego.de>