ALTV-393 v8::External::New can't be called with value == nullptr

[kin4stat-alt]

From v8 sources:

Local<External> v8::External::New(Isolate* isolate, void* value) {
  // Nullptr is not allowed here because serialization/deserialization of
  // nullptr external api references is not possible as nullptr is used as an
  // external_references table terminator, see v8::SnapshotCreator()
  // constructors.
  DCHECK_NOT_NULL(value);

this causes undefined behaviour and asserts in debug build and does not allow to continue code execution