JGIT Pull NoHeadException

When is try to execute the following method (uses JGIT library)

 private void pullRepo() throws  IOException,GitAPIException, WrongRepositoryStateException, InvalidConfigurationException, DetachedHeadException, InvalidRemoteException, CanceledException, RefNotFoundException, NoHeadException{
            Git  git = new Git(localRepo);
            git.pull().call();
    }

I get the following runtime exception:

org.eclipse.jgit.api.errors.NoHeadException: Pull on repository without HEAD currently not supported
at org.eclipse.jgit.api.PullCommand.call(PullCommand.java:161)

Does someone know how to solve this? The localRepo I use is the same as I use for the cloneRepository method ,which works perfectly.

thanks, bgvv1983