src: add not-weak DCHECK to PersistentToLocal::Strong

Refs: nodejs#38821 (comment)

PR-URL: nodejs#38875
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Bryan English <bryan@bryanenglish.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

Author: addaleax

src/util.h

@@ -760,6 +760,7 @@ class PersistentToLocal {
   template <class TypeName>
   static inline v8::Local<TypeName> Strong(
       const v8::PersistentBase<TypeName>& persistent) {
+    DCHECK(!persistent.IsWeak());
     return *reinterpret_cast<v8::Local<TypeName>*>(
         const_cast<v8::PersistentBase<TypeName>*>(&persistent));
   }