ffprobe failes to extract video bitrate for some avi files

[Shital]

ffprobe failes to extract video bitrate for the attached avi file
How to reproduce:

% fffprobe -v 9 -loglevel 99 sample.avi
ffprobe version 1.1 Copyright (c) 2007-2013 the FFmpeg developers
  built on Jan 10 2013 12:21:46 with gcc 3.4.6 (GCC) 20060404 (Red Hat 3.4.6-9)
  configuration: --enable-gpl --enable-version3 --enable-zlib --enable-bzlib --enable-pthreads --enable-libvorbis --enable-libtheora --enable-libspeex --enable-libmp3lame --enable-libxvid --enable-libx264 --enable-libopencore_amrwb --enable-libopencore_amrnb --enable-libvo-aacenc --enable-libvpx --enable-libgsm --extra-libs=-static
  libavutil      52. 13.100 / 52. 13.100
  libavcodec     54. 86.100 / 54. 86.100
  libavformat    54. 59.106 / 54. 59.106
  libavdevice    54.  3.102 / 54.  3.102
  libavfilter     3. 32.100 /  3. 32.100
  libswscale      2.  1.103 /  2.  1.103
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
[avi @ 0x92d8220] Format avi probed with size=2048 and score=100
[avi @ 0x92d8860] use odml:1
[avi @ 0x92d8220] File position before avformat_find_stream_info() is 428
[mpeg4 @ 0x92de6c0] Invalid and inefficient vfw-avi packed B frames detected
[avi @ 0x92d8220] All info found
[avi @ 0x92d8220] File position after avformat_find_stream_info() is 17206
Input #0, avi, from 'sample.avi':
  Metadata:
    encoder         : PENTAX Optio A30
  Duration: 00:00:17.43, start: 0.000000, bitrate: 234 kb/s
    Stream #0:0, 1, 1/30: Video: mpeg4 (DX50 / 0x30355844), yuv420p, 640x480 [SAR 1:1 DAR 4:3], 1/30, 30 tbr, 30 tbn, 30 tbc
    Metadata:
      title           : Video 
    Stream #0:1, 18, 1/4000: Audio: mp2 (P[0][0][0] / 0x0050), 48000 Hz, mono, s16p, 32 kb/s
    Metadata:
      title           : Audio 
[mpeg4 @ 0x92de6c0] detected 2 logical cores
[AVIOContext @ 0x92e08c0] Statistics: 65536 bytes read, 2 seeks

[Shital]

avi for which video bitrate is not extracted

[Carl Eugen Hoyos]

Also reproducible with "ffmpeg -i sample.avi".