src: suppress warning in src/node_env_var.cc

Initialise the superclass object in the copy constructor of mapKVStore

PR-URL: #31136
Refs: #18983
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Author: HarshithaKP

src/node_env_var.cc

@@ -47,7 +47,7 @@ class MapKVStore final : public KVStore {
   std::shared_ptr<KVStore> Clone(Isolate* isolate) const override;
 
   MapKVStore() = default;
-  MapKVStore(const MapKVStore& other) : map_(other.map_) {}
+  MapKVStore(const MapKVStore& other) : KVStore(), map_(other.map_) {}
 
  private:
   mutable Mutex mutex_;