memory leaks in vf_showfreqs

[Suhwan]

Summary of the bug:
There are memory leaks in ff_default_get_audio_buffer
How to reproduce:

% ffmpeg_g -y -i $PoC -filter_complex showfreqs -vbsf remove_extra -c ffvhuff tmp.dnxhd

ffmpeg version N-95554-g9d711a90fd Copyright (c) 2000-2019 the FFmpeg developers
built with clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)
configuration: --cc=clang --cxx=clang++ --ld=clang --enable-debug

Here's Valgrind log

==20368== HEAP SUMMARY:
==20368==     in use at exit: 286,808 bytes in 161 blocks
==20368==   total heap usage: 5,859 allocs, 5,698 frees, 386,379,085 bytes allocated
==20368== 
==20368== 286,808 (17,152 direct, 269,656 indirect) bytes in 32 blocks are definitely lost in loss record 10 of 10
==20368==    at 0x4C31E76: memalign (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==20368==    by 0x4C31F91: posix_memalign (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==20368==    by 0xF67AD2: av_malloc (mem.c:87)
==20368==    by 0xF67CD8: av_mallocz (mem.c:238)
==20368==    by 0xF5F0BA: av_frame_alloc (frame.c:191)
==20368==    by 0x2CF713: ff_frame_pool_get (framepool.c:201)
==20368==    by 0x2A2DE3: ff_default_get_audio_buffer (audio.c:73)
==20368==    by 0x400239: filter_frame (af_aresample.c:196)
==20368==    by 0x2BDE8B: ff_filter_frame_framed (avfilter.c:1084)
==20368==    by 0x2BDE8B: ff_filter_frame_to_filter (avfilter.c:1232)
==20368==    by 0x2BDE8B: ff_filter_activate_default (avfilter.c:1281)
==20368==    by 0x2BDE8B: ff_filter_activate (avfilter.c:1442)
==20368==    by 0x2C2747: push_frame (buffersrc.c:187)
==20368==    by 0x2C2747: av_buffersrc_add_frame_internal (buffersrc.c:261)
==20368==    by 0x2C2747: av_buffersrc_add_frame_flags (buffersrc.c:170)
==20368==    by 0x295AAC: ifilter_send_frame (ffmpeg.c:2187)
==20368==    by 0x295AAC: send_frame_to_filters (ffmpeg.c:2261)
==20368==    by 0x295D98: decode_audio (ffmpeg.c:2328)
==20368== 
==20368== LEAK SUMMARY:
==20368==    definitely lost: 17,152 bytes in 32 blocks
==20368==    indirectly lost: 269,656 bytes in 129 blocks
==20368==      possibly lost: 0 bytes in 0 blocks
==20368==    still reachable: 0 bytes in 0 blocks
==20368==         suppressed: 0 bytes in 0 blocks
==20368== 
==20368== For counts of detected and suppressed errors, rerun with: -v
==20368== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

Please confirm.
Thanks

[Suhwan]

poc

[James]

Fixed in 1aa4fc1ec204fabed5c40873b86751976167272f.