incorrect output with SBA-to-mono decoding at <=24.4 kbps

Basic info

• Commit SHA: 2b2b178a
• Platform:

Bug description

At lower bitrates, active W is enabled. However, the mono output mode only writes out the first transport channel and does not apply the upmix.

Ways to reproduce

(Clear steps or refer to a failing automated test, e.g. with a pipeline link)

./IVAS_cod -ism_sba 4 3 scripts/testv/stvISM1.csv scripts/testv/stvISM2.csv scripts/testv/stvISM3.csv scripts/testv/stvISM4.csv 24400 48 scripts/testv/stvOSBA_4ISM_3OA48c.wav bit
./IVas_dec mono 48 bit dec.wav