aura diff incorectly reports empty file

[RootLUG]

from reproducible builds:

  {
    "operation": "M",
    "diff": null,
    "similarity": 0.0,
    "a_ref": "click-8.1.3-py3-none-any.whl$click/py.typed",
    "a_md5": "d41d8cd98f00b204e9800998ecf8427e",
    "a_mime": "inode/x-empty",
    "a_size": 0,
    "b_ref": "click-8.1.3-py3-none-any.whl$click/py.typed",
    "b_md5": "d41d8cd98f00b204e9800998ecf8427e",
    "b_mime": "inode/x-empty",
    "b_size": 0
  },

empty file is reported as diffing, probably due to being empty which yields an empty disjoin set in the algorithm when comparing