false positive hook clang-format

This bug strikes again:

daniel@540U4C:~/workspace/qt5mixxx/build/Debug$ git commit -a
Check for byte-order marker..............................................Passed
Check for case conflicts.................................................Passed
Check JSON...........................................(no files to check)Skipped
Check for merge conflicts................................................Passed
Check Xml............................................(no files to check)Skipped
Check Yaml...........................................(no files to check)Skipped
Fix End of Files.........................................................Passed
Mixed line ending........................................................Passed
Trim Trailing Whitespace.................................................Passed
Don't commit to branch...................................................Passed
eslint...............................................(no files to check)Skipped
clang-format.............................................................Failed
- hook id: clang-format
- exit code: 2

Traceback (most recent call last):
  File "/home/daniel/bin/git-clang-format", line 579, in <module>
    main()
  File "/home/daniel/bin/git-clang-format", line 162, in main
    old_tree = create_tree_from_workdir(changed_lines)
  File "/home/daniel/bin/git-clang-format", line 343, in create_tree_from_workdir
    return create_tree(filenames, '--stdin')
  File "/home/daniel/bin/git-clang-format", line 396, in create_tree
    return tree_id
  File "/usr/lib/python2.7/contextlib.py", line 24, in __exit__
    self.gen.next()
  File "/home/daniel/bin/git-clang-format", line 463, in temporary_index_file
    os.remove(index_path)
OSError: [Errno 2] No such file or directory: '.git/clang-format-index'
`git write-tree` returned 128
fatal: Unable to create '/home/daniel/workspace/qt5mixxx/.git/clang-format-index.lock': Die Datei existiert bereits.

If no other git process is currently running, this probably means a
git process crashed in this repository earlier. Make sure no other git
process is running and remove the file manually to continue.
fatal: Unable to create '/home/daniel/workspace/qt5mixxx/.git/clang-format-index.lock': Die Datei existiert bereits.

If no other git process is currently running, this probably means a
git process crashed in this repository earlier. Make sure no other git
process is running and remove the file manually to continue.
error: `git update-index --add -z --stdin` failed
`git diff-files --name-status ` returned 128
fatal: ambiguous argument '': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

black................................................(no files to check)Skipped
flake8...............................................(no files to check)Skipped
qsscheck.............................................(no files to check)Skipped

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/9884