Update schema.js

Author: IslandRhythms

lib/schema.js

@@ -414,7 +414,7 @@ Schema.prototype._clone = function _clone(Constructor) {
   s.tree = clone(this.tree);
   // recursion is triggered here
   s.paths = Object.fromEntries(
-    Object.entries(this.paths).map(([key, value]) => ([key, value]))
+    Object.entries(this.paths).map(([key, value]) => ([key, value.$isSingleNested ? value.clone() : value]))
   );
   s.nested = clone(this.nested);
   s.subpaths = clone(this.subpaths);