Fix #10978: Advanced filters break permalinks

When using advanced filters with multiple items selected from a single
filter element, generation of permalinks fail due to passing an array to
rawurlencode(). Getting arrays from the parsing functions should be
expected and handled appropriately rather than blindly passing it to
rawurlencode().

core/string_api.php

@@ -267,7 +267,13 @@ function string_sanitize_url( $p_url, $p_return_absolute = false ) {
 
 		$t_clean_pairs = array();
 		foreach( $t_pairs as $t_key => $t_value ) {
-			$t_clean_pairs[] = rawurlencode( $t_key ) . '=' . rawurlencode( $t_value );
+			if ( is_array( $t_value ) ) {
+				foreach( $t_value as $t_value_each ) {
+					$t_clean_pairs[] .= rawurlencode( $t_key ) . '[]=' . rawurlencode( $t_value_each );
+				}
+			} else {
+				$t_clean_pairs[] = rawurlencode( $t_key ) . '=' . rawurlencode( $t_value );
+			}
 		}
 
 		if ( !empty( $t_clean_pairs ) ) {