“Catchable fatal error” how to solve?

Catchable fatal error: Object of class WP_Error could not be converted to string in /nfs/c06/h02/mnt/89623/domains/iamsteve.me/html/wp-includes/general-template.php on line 517

i can’t figure out for the life of me what i did wrong, as most of the modifications to my site i had been doing were only to do with the blog posts page

if you look at https://iamsteve.me – error
if you look at https://iamsteve.me/blog – fine

so i undone plugins i installed, removed some codes i added, checked the general-template.php line 517 – didn’t seem out of the ordinary heres the code;

// Determines position of the separator and direction of the breadcrumb
	if ( 'right' == $seplocation ) { // sep on right, so reverse the order
		$title_array = explode( $t_sep, $title );
		$title_array = array_reverse( $title_array );          // LINE 517
		$title = implode( " $sep ", $title_array ) . $prefix;
	} else {
		$title_array = explode( $t_sep, $title );
		$title = $prefix . implode( " $sep ", $title_array );
	}

	$title = apply_filters('wp_title', $title, $sep, $seplocation);

	// Send it out
	if ( $display )
		echo $title;
	else
		return $title;