comment_max_links causes confusion when zero

[tellyworth]

1. go to Settings/Discussion

2. Uncheck "An administrator must always approve the comment "

3. Set "Hold a comment in the queue if it contains 0 or more links."

4. Post a comment

Expected: the comment should not be moderated.

Actual: the comment goes into the moderation queue.

Technically that's not incorrect, but it's confusing - the moderation setting should take precedence and comment_max_links should be ignored if it's zero.

[azaozz]

(In [8833]) Ignore comment_max_links option when zero, props tellyworth, fixes #7699