Prevent segfault on data stream template

[dotysan]

I was wrongly attempting to copy a data stream using add_stream_from_template() and got a segfault instead of a useful response. This patch/test resolves.

The segfault occurs on assigning None.codec or None.name to codec_obj: Codec.

[dotysan]

OK, clearly I'm going about this wrong.

mypy av tests
tests/test_streams.py:160: error: Value of type variable "_StreamT" of "add_stream_from_template" of "OutputContainer" cannot be "DataStream"  [type-var]
Found 1 error in 1 file (checked 88 source files)
make: *** [Makefile:34: lint] Error 1

Why doesn't this in output.pyi prevent the segfault in the first place?!?

class OutputContainer(Container):
    ...
    def add_stream_from_template(
        self, template: _StreamT, opaque: bool | None = None, **kwargs
    ) -> _StreamT: ...

[WyattBlue]

.pyi files are just type stubs. They help mypy but don't affect behavior

[dotysan]

Is there something I can do to get that Windoze smoke test to pass?

[WyattBlue]

Windows failing seems unrelated. If you can fix this, make a separate PR