Remuxing amr does not work

[necros]

Summary of the bug:
Output file is corrupted (stripped data)
How to reproduce:

% ffmpeg.exe -i "test.3gp" -vcodec copy -acodec copy -map 0 -map_metadata -1 "out.3gp"
ffmpeg version git-2020-07-24-21442a8 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9.3.1 (GCC) 20200621

[necros]

source file

[necros]

win64 binary on win10x64 2004

[Carl Eugen Hoyos]

For future tickets: Please remember to always provide the command line you tested together with the complete, uncut console output.
Not a regression afaict.

$ ffmpeg -i test.3gp -c copy out.3gp
ffmpeg version N-98574-gfa3da243e6 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9 (SUSE Linux)
  configuration: --enable-gpl --enable-gnutls --enable-libmp3lame --enable-libx264 --enable-libx265 --enable-libdav1d --enable-libvpx --enable-libopus --enable-libxml2 --enable-libwebp --enable-librav1e --enable-libfreetype --enable-libass
  libavutil      56. 57.100 / 56. 57.100
  libavcodec     58. 97.102 / 58. 97.102
  libavformat    58. 49.100 / 58. 49.100
  libavdevice    58. 11.101 / 58. 11.101
  libavfilter     7. 87.100 /  7. 87.100
  libswscale      5.  8.100 /  5.  8.100
  libswresample   3.  8.100 /  3.  8.100
  libpostproc    55.  8.100 / 55.  8.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.3gp':
  Metadata:
    major_brand     : 3gp5
    minor_version   : 256
    compatible_brands: isom3gp53gp4
    creation_time   : 2019-07-29T00:11:54.000000Z
  Duration: 00:00:08.60, start: 0.000000, bitrate: 84 kb/s
    Stream #0:0(und): Audio: amr_nb (samr / 0x726D6173), 8000 Hz, mono, flt, 12 kb/s (default)
    Metadata:
      creation_time   : 2019-07-29T00:11:54.000000Z
      handler_name    : Core Media Audio
    Stream #0:1(und): Video: h263 (s263 / 0x33363273), yuv420p, 176x144 [SAR 12:11 DAR 4:3], 69 kb/s, 10 fps, 10 tbr, 600 tbn, 29.97 tbc (default)
    Metadata:
      creation_time   : 2019-07-29T00:11:54.000000Z
      handler_name    : Core Media Video
[3gp @ 0x2d9efc0] track 1: codec frame size is not set
Output #0, 3gp, to 'out.3gp':
  Metadata:
    major_brand     : 3gp5
    minor_version   : 256
    compatible_brands: isom3gp53gp4
    encoder         : Lavf58.49.100
    Stream #0:0(und): Video: h263 (s263 / 0x33363273), yuv420p, 176x144 [SAR 12:11 DAR 4:3], q=2-31, 69 kb/s, 10 fps, 10 tbr, 19200 tbn, 600 tbc (default)
    Metadata:
      creation_time   : 2019-07-29T00:11:54.000000Z
      handler_name    : Core Media Video
    Stream #0:1(und): Audio: amr_nb (samr / 0x726D6173), 8000 Hz, mono, flt, 12 kb/s (default)
    Metadata:
      creation_time   : 2019-07-29T00:11:54.000000Z
      handler_name    : Core Media Audio
Stream mapping:
  Stream #0:1 -> #0:0 (copy)
  Stream #0:0 -> #0:1 (copy)
Press [q] to stop, [?] for help
[3gp @ 0x2d9efc0] fatal error, input is not a single packet, implement a AVParser for it
av_interleaved_write_frame(): Operation not permitted
[3gp @ 0x2d9efc0] fatal error, input is not a single packet, implement a AVParser for it
Error writing trailer of out.3gp: Operation not permitted
frame=    1 fps=0.0 q=-1.0 Lsize=       2kB time=00:00:00.39 bitrate=  50.3kbits/s speed=4.82e+03x    
video:2kB audio:1kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Conversion failed!