Index: classes/tggr-media-source.php
===================================================================
--- classes/tggr-media-source.php	(revision 1583955)
+++ classes/tggr-media-source.php	(working copy)
@@ -159,11 +159,12 @@
 		public static function sort_by_author( $query_vars ) {
 			$class = get_called_class();
 
-			if ( array_key_exists( 'orderby', $query_vars ) && $class::POST_TYPE_SLUG == $query_vars['post_type'] ) {
-				if ( 'Author' == $query_vars['orderby'] ) {
-					$query_vars['orderby']  = 'meta_value';
-					$query_vars['meta_key'] = self::get_author_username_key( $class );
-				}
+			if ( isset( $query_vars['orderby'], $query_vars['post_type'] ) &&
+			     $class::POST_TYPE_SLUG == $query_vars['post_type'] &&
+			     'Author' == $query_vars['orderby'] ) {
+
+				$query_vars['orderby']  = 'meta_value';
+				$query_vars['meta_key'] = self::get_author_username_key( $class );
 			}
 
 			return $query_vars;
Index: classes/tggr-source-flickr.php
===================================================================
--- classes/tggr-source-flickr.php	(revision 1583955)
+++ classes/tggr-source-flickr.php	(working copy)
@@ -69,7 +69,10 @@
 			add_filter( 'manage_edit-' . self::POST_TYPE_SLUG . '_columns',             __CLASS__ . '::add_columns'            );
 			add_filter( 'manage_edit-' . self::POST_TYPE_SLUG . '_sortable_columns',    __CLASS__ . '::add_columns'            );
 			add_action( 'manage_' .      self::POST_TYPE_SLUG . '_posts_custom_column', __CLASS__ . '::display_columns', 10, 2 );
-			add_filter( 'request',                                                      __CLASS__ . '::sort_by_author'         );
+
+			if ( is_admin() ) {
+				add_filter( 'request', __CLASS__ . '::sort_by_author' );
+			}
 		}
 
 		/**
Index: classes/tggr-source-google.php
===================================================================
--- classes/tggr-source-google.php	(revision 1583955)
+++ classes/tggr-source-google.php	(working copy)
@@ -68,7 +68,10 @@
 			add_filter( 'manage_edit-' . self::POST_TYPE_SLUG . '_columns',             __CLASS__ . '::add_columns'            );
 			add_filter( 'manage_edit-' . self::POST_TYPE_SLUG . '_sortable_columns',    __CLASS__ . '::add_columns'            );
 			add_action( 'manage_' .      self::POST_TYPE_SLUG . '_posts_custom_column', __CLASS__ . '::display_columns', 10, 2 );
-			add_filter( 'request',                                                      __CLASS__ . '::sort_by_author'         );
+
+			if ( is_admin() ) {
+				add_filter( 'request', __CLASS__ . '::sort_by_author' );
+			}
 		}
 
 		/**
Index: classes/tggr-source-instagram.php
===================================================================
--- classes/tggr-source-instagram.php	(revision 1583955)
+++ classes/tggr-source-instagram.php	(working copy)
@@ -72,7 +72,10 @@
 			add_filter( 'manage_edit-' . self::POST_TYPE_SLUG . '_columns',             __CLASS__ . '::add_columns'            );
 			add_filter( 'manage_edit-' . self::POST_TYPE_SLUG . '_sortable_columns',    __CLASS__ . '::add_columns'            );
 			add_action( 'manage_' .      self::POST_TYPE_SLUG . '_posts_custom_column', __CLASS__ . '::display_columns', 10, 2 );
-			add_filter( 'request',                                                      __CLASS__ . '::sort_by_author'         );
+
+			if ( is_admin() ) {
+				add_filter( 'request', __CLASS__ . '::sort_by_author' );
+			}
 		}
 
 		/**
Index: classes/tggr-source-twitter.php
===================================================================
--- classes/tggr-source-twitter.php	(revision 1583955)
+++ classes/tggr-source-twitter.php	(working copy)
@@ -72,7 +72,10 @@
 			add_filter( 'manage_edit-' . self::POST_TYPE_SLUG . '_columns',             __CLASS__ . '::add_columns'            );
 			add_filter( 'manage_edit-' . self::POST_TYPE_SLUG . '_sortable_columns',    __CLASS__ . '::add_columns'            );
 			add_action( 'manage_' .      self::POST_TYPE_SLUG . '_posts_custom_column', __CLASS__ . '::display_columns', 10, 2 );
-			add_filter( 'request',                                                      __CLASS__ . '::sort_by_author'         );
+
+			if ( is_admin() ) {
+				add_filter( 'request', __CLASS__ . '::sort_by_author' );
+			}
 		}
 
 		/**