Fix for #2776: 'null' response to Invoke when using AspNetCore integration package

[beauzeaux]

Fixed issue where the body of invokes with no response was 'null' rather than an empty body. This was causing all the TeamsActivityHandler delegates that didn't have a payload response to an invoke to fail in-flight on returning to Teams as one of the intermediaries attempts to parse the body as JSON if present.

[coveralls]

Pull Request Test Coverage Report for Build 84685

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-1.4%) to 76.014%

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Totals
Change from base Build 84533:	-1.4%
Covered Lines:	7926
Relevant Lines:	10427

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💛 - Coveralls

[johnataylor]

Looks like a bug, and this fix looks good, we should take this fix.

However, one note this is in the old style ASP integration layer. The new style (i.e. using the BotFrameworkHttpAdapter class) provides a more natural and more flexible integration with ASP that sits much better with the dotnet core dependency injection.

[beauzeaux]

I'll go ahead and merge then.

However, one note this is in the old style ASP integration layer. The new style (i.e. using the BotFrameworkHttpAdapter class) provides a more natural and more flexible integration with ASP that sits much better with the dotnet core dependency injection

I'm curious why this is the case, but we can discuss in a more appropriate channel than a PR thread.

Edit: I'm a fool - not used to this when I'm not the maintainer of the repository. Apologies for the close / reopen.