botframework-sdk: [Skype] EndConversation fails with "Unknown activity type" exception

Bot Info

• Bot handle:
• App ID:
• SDK Platform: .NET
• SDK Version: 3.9.1
• Active Channels: Skype, Facebook
• Deployment Environment: Azure App Service

Issue Description

After a use case has been completed, we call context.EndConversation("end of conversation") to reset stack and conversation data.

• In Facebook, it resets the stack and clears the data, and no exception occures => OK
• In Skype, it resets the stack and clears the data, but an exception is thrown

“Unknown activity type”

Resulting in a “Sorry my bot code having an issue…” (btw, regardless I specified a custom message).

Code Example

Reproduction Steps

1. Create a simple bot and call context.EndConversation("end of conversation");
2. Deploy to skype and test

Expected Behavior

In skype, it should not throw an exception.

Actual Results

It throws an exception > “Unknown activity type”

Workaround

Placing that line in a try-catch block does not help because the event triggers a scorable. A workaround for me could be, duplicating this code and try-catch here, but I hope for a better suggestion or fix 😉