avcodec/g2meet: check framebuf has been allocated before use

Fixes null pointer dereference

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
g2meet: Check cursor parameters before writing them in the context

Fixes out of array access

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
g2meet: fix typo in height comparission

Fixes CID1030349
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
id2v2: check the return value of decode_str()

Fixes CID1030348
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Insert a newline before showing embedded svq1 messages.

Messages may start with a carriage return.