MSAN fixes for STEREO, OSBA High MLD fix

[x] Fix for High MLD issue for a OSBA stream
[x] MSAN fixes - STEREO streams
[x] Fixed crash in ltv48_MC512.wav_Multi_channel_5_1_2_bitrate_switching_from_13_2_kbps_to_512_kbps_48kHz_in_16kHz_out_BINAURAL_ROOM_out.192

EVS 26.444 BE test passes.
pytests results: 588 failed, 381 skipped

MLD scores:
Original inputs:
MLD > 10: 122; Out of these, 51 cases are PLC
MLD > 5 : 98
MLD < 5 : 368

+10dB inputs:
MLD > 10: 315
MLD > 5 : 113
MLD < 5 : 160

-10dB inputs:
MLD > 10: 70
MLD > 5 : 70
MLD < 5 : 448