Fix a memory leak in GroupAV

[nurupo]

Clang's scan-build has identified two potential memory leaks in groupav.c. Looks like there were cases when the decode_audio_packet() function would return without freeing the allocated memory, which is fixed by this PR.

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This change is 

[iphydf]

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Review status: 0 of 1 files reviewed at latest revision, 1 unresolved discussion, some commit checks failed.

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toxav/groupav.c, line 373 at r1 (raw file):

        if (out_audio_samples <= 0) {
            free(out_audio);

(I love me some code duplication..)

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Comments from Reviewable

[GrayHatter]

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Reviewed 1 of 1 files at r1.
Review status: all files reviewed at latest revision, 1 unresolved discussion, some commit checks failed.

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Comments from Reviewable