With some malformed email address list, the parser for email groups raises an `IndexError` instead of the correct `HeaderParseError`.

This results in a complete failure to parse the email while it is still preferable to just ignore the malformed header.

An example of such a malformed list is this:
`To: :Foo <foo@example.com> <bar@example.com>`

In case an address email header contains and empty string, the tokenizer return a BareQuotedString
which is also a TokenList, but this list is empty and the parser fails to check this and insteads raises an IndexError.

For example an email with this header will trigger the IndexError:
ReplyTo: ""

Disregard my last message, I posted it in the wrong bug report by mistake.
Sorry about the noise

I don't think this is an issue anymore, I guess this was fixed as a part of some other PR.

I tested this out on a recent branch:

   >>> import email
   >>> msg = email.message_from_string('From: Abhilash <maxking@email.com> <Another@some.com>')
   >>> msg['From'] 
   'Abhilash <maxking@email.com> <Another@some.com>'

@david, @barry: I think we can close this issue.

Based on @maxking's comment, I'm going to close this issue.  Thank you!

The fact that the original report mentions HeaderParserError implies that the new API is being used, though the report didn't make that clear.  The problem still exists:

>>> m = message_from_string("To: :Foo <foo@example.com> <bar@example.com>\n\n", policy=default)
>>> m['To']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/rdmurray/python/p38/Lib/email/message.py", line 391, in __getitem__
    return self.get(name)
  File "/home/rdmurray/python/p38/Lib/email/message.py", line 471, in get
    return self.policy.header_fetch_parse(k, v)
  File "/home/rdmurray/python/p38/Lib/email/policy.py", line 163, in header_fetch_parse
    return self.header_factory(name, value)
  File "/home/rdmurray/python/p38/Lib/email/headerregistry.py", line 602, in __call__
    return self[name](name, value)
  File "/home/rdmurray/python/p38/Lib/email/headerregistry.py", line 197, in __new__
    cls.parse(value, kwds)
  File "/home/rdmurray/python/p38/Lib/email/headerregistry.py", line 343, in parse
    groups.append(Group(addr.display_name,
  File "/home/rdmurray/python/p38/Lib/email/_header_value_parser.py", line 315, in display_name
    return self[0].display_name
  File "/home/rdmurray/python/p38/Lib/email/_header_value_parser.py", line 382, in display_name
    return self[0].display_name
  File "/home/rdmurray/python/p38/Lib/email/_header_value_parser.py", line 564, in display_name
    if res[0].token_type == 'cfws':
IndexError: list index out of range

New changeset 09a1872a8007048dcdf825a476816c5e3498b8f8 by Miss Islington (bot) (Abhilash Raj) in branch 'master':
bpo-32178: Fix IndexError trying to parse 'To' header starting with ':'. (GH-15044)
https://github.com/python/cpython/commit/09a1872a8007048dcdf825a476816c5e3498b8f8

New changeset 9500bbe9372f6080decc49d2fd9365f0b927a0e2 by Miss Islington (bot) in branch '3.8':
bpo-32178: Fix IndexError trying to parse 'To' header starting with ':'. (GH-15044)
https://github.com/python/cpython/commit/9500bbe9372f6080decc49d2fd9365f0b927a0e2

New changeset dec231a73c2a463b29f19c4e8357602c10a68856 by Miss Islington (bot) in branch '3.7':
bpo-32178: Fix IndexError trying to parse 'To' header starting with ':'. (GH-15044)
https://github.com/python/cpython/commit/dec231a73c2a463b29f19c4e8357602c10a68856