the git clone is empty? why this happens

This particular git repository seems to not have any contents on its master branch, which is the branch git checks out by default. It does however have another branch:

% git branch -a
* master
  remotes/origin/HEAD -> origin/master
  remotes/origin/android-msm-2.6.35
  remotes/origin/master

So if you check out this branch:

% git checkout android-msm-2.6.35
Checking out files: 100% (33866/33866), done.
Branch android-msm-2.6.35 set up to track remote branch android-msm-2.6.35 from origin.
Switched to a new branch 'android-msm-2.6.35'

then there’s also content in the working tree.