Ensure 'found_posts' is correct when no limit queries are in use

[r-a-y]

Currently, if a no limit query is set for WP_Query, the returned 'found_posts' property is zero instead of the number of posts.

'found_posts' is set to 'NA' here:

advanced-post-cache/advanced-post-cache.php

Lines 200 to 201 in c46b2d9

	if ( empty( $limits ) || ( isset( $query->query_vars['no_found_rows'] ) && $query->query_vars['no_found_rows'] ) )
	$this->found_posts = 'NA';

And never redeclared.

So when advanced-post-cache gets to returning the found posts count:

advanced-post-cache/advanced-post-cache.php

Lines 230 to 231 in c46b2d9

	if ( $this->found_posts && is_array( $this->all_post_ids ) ) // is cached
	return (int) $this->found_posts;

It returns 0 because of (int) 'NA'.

This PR fixes this by returning the count of the cached post IDs if 'found_posts' is a no limit query ('NA'). This is important for plugins doing checks against 'found_posts' and are anticipating a non-zero count. For example, bbPress does such a check here: https://github.com/bbpress/bbPress/blob/b772b4503991e3d55a34a4683a1f84e60decbce1/src/includes/replies/template.php#L212-L213

This addresses #4.

[tomjn]

You're right, this value should be 0 not NA. 0 is what WP_Query uses

As for BBPress instead of:

	// Only add reply to if query returned results
	if ( ! empty( $bbp->reply_query->found_posts ) ) {

It should be:

	// Only add reply to if query returned results
	if ( $bbp->reply_query->have_posts() ) {

[r-a-y]

found_posts should not return 0 for no-limit queries. It should always return the proper post count. Check the value when this plugin isn't activated.

Switching to posts_pre_query (#10) and adding the proper 'found_posts' count property would also fix this if implemented correctly.