bbp_get_topic_last_reply_id() returns the topic id when the topic does not have any replies

[netweb]

// Create a forum
$forum_id = bbp_insert_forum( array(
	'post_title'   => 'forum_title',
	'post_content' => 'forum_content'
) );

// Create a topic
$topic_id = bbp_insert_topic( array(
	'post_title'   => 'topic_title',
	'post_content' => 'topic_content'
) );
var_dump( $forum_id );
var_dump( bbp_get_forum_last_topic_id( $forum_id ) );
var_dump( $topic_id );
var_dump( bbp_get_topic_last_reply_id( $topic_id ) );

Returns: int(59) int(0) int(60) int(60)
Expected: int(59) int(0) int(60) int(0)

Both functions create their correct meta values _bbp_last_topic_id and _bbp_last_reply_id with value 0

​https://bbpress.trac.wordpress.org/browser/trunk/src/includes/forums/template.php?annotate=blame#L891
​https://bbpress.trac.wordpress.org/browser/trunk/src/includes/topics/template.php?annotate=blame#L2018

[netweb]

Patch includes a fix and unit test documenting the issue.

Note: Need to consider a better file name, file location and function name for the included unit tests ;)

[johnjamesjacoby]

This might break other things upstream, specifically single topics where both topics and replies are in the same loop, and the topic does not have any replies.

[johnjamesjacoby]

In 5842:

IDs: Some reply functions still default to their topics if no replies are present. This functionality has slowly been removed over time and built into respective functions. In this changeset, we remove those leftover assignments and update a few phpdoc descriptions as needed.

Hat-tip netweb. See #2806.

[johnjamesjacoby]

In 5844:

Add unit test for last topic & reply ID's for topics & forums. Fixes #2806. Props netweb.

[netweb]

In 5872:

Tests: Include bbp_get_forum_last_reply_id() assertions in test_bbp_get_forum_and_topic_last_topic_id_and_last_reply_id() missed in r5844

See #2806