wordpress - Why is $wp_query->post unset during 404? -

i using plugin called connections. when 404 occurs (for reason, i.e. page doesn't exist accessed via browser) custom post callback filter, specified in plugin's code breaks, $wp_query->post unset. complaint trying property of non-object when $wp_query->post->id accessed. expect.

i have disabled other plugins , gone twenty fifteen theme issue still occurs. on clean install problem doesn't occur. doesn't make sense me. if it's not plugin or theme issue , it's not in wordpress core issue? corrupt database? (everything else seems working fine).

the filter callback here:

public static function filterposttitle( $title, $id = 0 ) {    global $wp_query, $post, $connections;     // added: if add line problem goes away.    if ( is_404() ) return $title;     // whether or not filter page title current directory location.    if ( ! cnsettingsapi::get( 'connections', 'connections_seo', 'page_title' ) ) return $title;     // if uncomment next 2 lines , comment out following line of code, problem goes away.    //$post_id = get_queried_object_id();    //if ( ! is_object( $post ) || $post_id != $id || ! self::$filterpermalink ) return $title;     if ( ! is_object( $post ) || $wp_query->post->id != $id || ! self::$filterpermalink ) return $title; 

if add following check @ start of function problem goes away (again we'd expect):

if ( ! isset( $wp_query->post ) || ! isset( $wp_query->post->id ) ) return $title; 

i have printed out backtraces give me clues, backtraces don't seem give many clues global variable $wp_query @ fault. reminder why globals bad practise... poor show wordpress. globals make debugging nightmare. global variable changed? don't know.

the filter callback set follows:

add_filter( 'the_title', array( __class__, 'filterposttitle' ), 10, 2 ); 

the developer of plugin (maybe rightly so) thinks problem lies outside of plugin.

question: why $wp_query->post unset @ time of callback being triggered? should $wp_query->post set time 'the_title' filter callback triggered?

as may guess new wordpress. it's fantastic... not fan of global variables though... big no-no.

it's not $wp_query->post unset during 404...but rather it's never set @ all. in fact, $wp_query->post unset new instances of wp_query, when initialized. let's look @ source:

/**  * initiates object properties , sets default values.  *  * @since 1.5.0  * @access public  */ public function init() {     unset($this->posts);     unset($this->query);     $this->query_vars = array();     unset($this->queried_object);     unset($this->queried_object_id);     $this->post_count = 0;     $this->current_post = -1;     $this->in_the_loop = false;     unset( $this->request );     unset( $this->post );  // unset     unset( $this->comments );     unset( $this->comment );     $this->comment_count = 0;     $this->current_comment = -1;     $this->found_posts = 0;     $this->max_num_pages = 0;     $this->max_num_comment_pages = 0;     $this->init_query_flags(); } 

next, query parsed, , if there's error:

if ( '404' == $qv['error'] )     $this->set_404(); 

the 404 status set, , $wp_query->post never populated/set.