avcodec/iff: warn about truncated input to decode_byterun() and clear remaining output

Fixes use of uninitialized memory
Fixes: msan_uninit-mem_7fe205e395ed_8988_test.iff
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avformat/nistspheredec: check sscanf() success before using the result

Fixes use of uninitialized memory
Fixes: msan_uninit-mem_7f935c3c6c1a_7413_nist_pcms8.nist
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
remuxing .opus files to .webm codec->delay must be copied too

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avformat/sierravmd: Check avio_read return value

Fixes use of uninitialized memory
Fixes: msan_uninit-mem_7f82af392dae_1848_HR060606.VMD
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>