fixes #248 Convert to a tree on omt clone if it must support marks

util/omt.cc

@@ -207,6 +207,9 @@ void omt<omtdata_t, omtdataout_t, supports_marks>::clone(const omt &src) {
         src.fill_array_with_subtree_values(&this->d.a.values[0], src.d.t.root);
     }
     this->d.a.num_values = src.size();
+    if (supports_marks) {
+        this->convert_to_tree();
+    }
 }
 
 template<typename omtdata_t, typename omtdataout_t, bool supports_marks>