Issue 5040 - fix saving of allowed_connection_type preference

src/FilterEngine.cpp

Index: src/FilterEngine.cpp
diff --git a/src/FilterEngine.cpp b/src/FilterEngine.cpp
index 5c1a495619c76e0b51a886b9116807789b135c9a..42b7b0b5a2e8a3960c46451b575d3b115c330115 100644
--- a/src/FilterEngine.cpp
+++ b/src/FilterEngine.cpp
@@ -485,13 +485,13 @@ void FilterEngine::RemoveFilterChangeCallback()
 
 void FilterEngine::SetAllowedConnectionType(const std::string* value)
 {
-  SetPref("allowed_connection_type", value ? jsEngine->NewValue(*value) : nullptr);
+  SetPref("allowed_connection_type", value ? jsEngine->NewValue(*value) : jsEngine->NewValue(""));
 }
 
 std::unique_ptr<std::string> FilterEngine::GetAllowedConnectionType() const
 {
    auto prefValue = GetPref("allowed_connection_type");
-   if (prefValue->IsUndefined())
+   if (prefValue->AsString().empty())
      return nullptr;
    return std::unique_ptr<std::string>(new std::string(prefValue->AsString()));
 }