Some case Failed when run ext_test

[Alanscut]

Hi @stefankoegl , when I run the external tests json-patch-tests, some case failed, I think some of them are bugs, others are due to unreasonable assertions.
here is the list:

• 1: pass only when changing add to replace -- not sure if it is a bug

    { "comment": "replace array document with object document?",
      "doc": [],
      "patch": [{"op": "add", "path": "", "value": {}}],
      "expected": {} }

• 2: failed with KeyError: 'path' before entering the assertion -- unreasonable assertion

    { "comment": "missing 'path' parameter",
      "doc": {},
      "patch": [ { "op": "add", "value": "bar" } ],
      "error": "missing 'path' parameter" }

• 3: failed with TypeError: expected string or bytes-like object before entering the assertion -- unreasonable assertion

      { "comment": "'path' parameter with null value",
        "doc": {},
        "patch": [ { "op": "add", "path": null, "value": "bar" } ],
        "error": "null is not valid value for 'path'" }

-4: index leading with zero should failed but success -- bug

      { "comment": "test with bad array number that has leading zeros",
        "doc": ["foo", "bar"],
        "patch": [{"op": "test", "path": "/00", "value": "foo"}],
        "error": "test op should reject the array value, it has leading zeros" },
  
      { "comment": "test with bad array number that has leading zeros",
        "doc": ["foo", "bar"],
        "patch": [{"op": "test", "path": "/01", "value": "bar"}],
        "error": "test op should reject the array value, it has leading zeros" }