botbuilder-dotnet: QnAMakerOptions doesn't reset filters values

Version

4.3.2

Describe the bug

We are working with a bot using QnAMaker class from Microsoft.Bot.Builder.AI.QnA StrictFilters from QnAMakerOptions doesn’t work with an empty value after using it with a filter

To Reproduce

Call GetAnswersAsync using an QnAMakerOptions without any StrictFilter

var options1 = new QnAMakerOptions
{
    Top = 10,
    ScoreThreshold = 0.6f,
};
var response = await _services.QnAServices[QnAMakerKey].GetAnswersAsync(turnContext, options1);
if (response != null && response.Length > 0)
{
    await turnContext.SendActivityAsync($"QnA Results: {response.Length}");
}

Now, make another call with a StrictFilter

var options2 = new QnAMakerOptions
{
    Top = 10,
    ScoreThreshold = 0.6f,
    StrictFilters = new Metadata[] { new Metadata() { Name = "Topic", Value = "sharepoint" } },
};
var response2 = await _services.QnAServices[QnAMakerKey].GetAnswersAsync(turnContext, options2);
if (response2 != null && response2.Length > 0)
{
    await turnContext.SendActivityAsync($"QnA Results: {response2.Length}");
}

Repeat the first call without and StrictFilter

var options3 = new QnAMakerOptions
{
    Top = 10,
    ScoreThreshold = 0.6f,
};
var response3 = await _services.QnAServices[QnAMakerKey].GetAnswersAsync(turnContext, options3);
if (response3 != null && response3.Length > 0)
{
    await turnContext.SendActivityAsync($"QnA Results: {response3.Length}");
}

Expected behavior

From the third call, I expected to have the same results we had on the first one, but for any reason the StrictFilters didn’t reset its values well.

Screenshots

[bug]