Index: wp-admin/includes/misc.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- wp-admin/includes/misc.php	(revision 921e131eae45801b8fdb1ecfceb5d7839fdfd509)
+++ wp-admin/includes/misc.php	(date 1522703361000)
@@ -196,10 +196,12 @@
  * @since 1.5.0
  *
  * @global WP_Rewrite $wp_rewrite
+ *
+ * @return bool
  */
 function save_mod_rewrite_rules() {
 	if ( is_multisite() ) {
-		return;
+		return false;
 	}
 
 	global $wp_rewrite;