fix: update typing inspect get_origin check

[hallvictoria]

Description

Previously, this was the check in get_function_return_type:

if typing_inspect.is_generic_type(
                    return_anno) and typing_inspect.get_origin(
                    return_anno).__name__ == 'Out':

If typing_inspect.get_origin(return_anno) returned None, there would be an error thrown saying AttributeError: 'NoneType' object has no attribute '__name__'.

This change introduces a new check to ensure that typing_inspect.get_origin(return_anno) is not None before checking the __name__ property.

Fixes https://github.com/Azure/azure-functions-python-worker/issues/1688

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