Fix bugs, use plural post slugs, move actions and filters into hooks folder

admin/hooks/post-thumbnail-html.php

@@ -0,0 +1,14 @@
+<?php
+function sportspress_post_thumbnail_html( $html, $post_id, $post_thumbnail_id, $size, $attr ) {
+    if( empty ( $html ) && in_array( get_post_type( $post_id ), array( 'sp_team', 'sp_tournament' ) ) ) {
+		$parents = get_post_ancestors( $post_id );
+		foreach ( $parents as $parent ) {
+			if( has_post_thumbnail( $parent ) ) {
+				$html = get_the_post_thumbnail( $parent, $size, $attr );
+				break;
+			}
+		}
+    }
+    return $html;
+}
+add_filter( 'post_thumbnail_html', 'sportspress_post_thumbnail_html', 10, 5 );