memory leaks are detected in av_frame_alloc

[Suhwan]

Summary of the bug:
memory leaks are detected
How to reproduce:

% ffmpeg_g -y -i $PoC -filter_complex reverse -target vcd -loglevel 0 -map 0 -vframes 94 -aframes 45 -r 32 -ab 991k -ar 48000 -ac 29 -b:v 711k -strict 0 tmp.g726

ffmpeg version N-95389-gdd01947397 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

==15573== HEAP SUMMARY:
==15573==     in use at exit: 14,638 bytes in 20 blocks
==15573==   total heap usage: 2,581 allocs, 2,561 frees, 1,418,329 bytes allocated
==15573== 
==15573== 14,606 (536 direct, 14,070 indirect) bytes in 1 blocks are definitely lost in loss record 16 of 16
==15573==    at 0x9D3CE76: memalign (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==15573==    by 0x9D3CF91: posix_memalign (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==15573==    by 0x590EC79: av_malloc (mem.c:87)
==15573==    by 0x590EC79: av_mallocz (mem.c:238)
==15573==    by 0x58E2E0D: av_frame_alloc (frame.c:191)
==15573==    by 0x5F4120: av_buffersrc_add_frame_internal (buffersrc.c:237)
==15573==    by 0x5F2E2D: av_buffersrc_add_frame_flags (buffersrc.c:170)
==15573==    by 0x4CAD0F: ifilter_send_frame (ffmpeg.c:2186)
==15573==    by 0x4CAD0F: send_frame_to_filters (ffmpeg.c:2260)
==15573==    by 0x4A076B: decode_video (ffmpeg.c:2459)
==15573==    by 0x4A076B: process_input_packet (ffmpeg.c:2613)
==15573==    by 0x4B9FE7: process_input (ffmpeg.c:4303)
==15573==    by 0x48D59A: transcode_step (ffmpeg.c:4628)
==15573==    by 0x48D59A: transcode (ffmpeg.c:4682)
==15573==    by 0x487D53: main (ffmpeg.c:4884)
==15573== 
==15573== LEAK SUMMARY:
==15573==    definitely lost: 536 bytes in 1 blocks
==15573==    indirectly lost: 14,070 bytes in 18 blocks
==15573==      possibly lost: 0 bytes in 0 blocks
==15573==    still reachable: 32 bytes in 1 blocks
==15573==         suppressed: 0 bytes in 0 blocks
==15573== Reachable blocks (those to which a pointer was found) are not shown.
==15573== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==15573== 
==15573== For counts of detected and suppressed errors, rerun with: -v
==15573== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

Please confirm.
Thanks

[Suhwan]

poc