[PATCH v2 0/1] MR4198: mf/tests: Test hr before checking propvar.pwszVal.

[Rémi Bernon]

Wine-Bug: https://bugs.winehq.org//show_bug.cgi?id=55588

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  v2: mf/tests: Avoid crashing if MF_BYTESTREAM_EFFECTIVE_URL is missing.
 
https://gitlab.winehq.org/wine/wine/-/merge_requests/4198