Crash in Unified Stereo with frameloss

Basic info

• Commit SHA: 34c6b03f
• Platform: all

Bug description

Decoder runs into assertion when decoding TCX bitstream:

Assertion failed: (st->next_bit_pos - start_bit_pos + rest_bits <= 0), function RCcontextMapping_decode2_no_mem_s17_LCS, file lib_dec/ACcontextMapping_dec.c, line 638.

Was discovered from Sanitizer pipeline (https://forge.3gpp.org/rep/ivas-codec-pc/ivas-codec/-/jobs/36912), but is a general bug (shows up without needing to build with the sanitizers).

Ways to reproduce

git checkout 34c6b03f427672076ad7fa2da97920638f431888
make clean
make -j

# use attached bitstream from below
./IVAS_dec stereo 32 test_stereo_cut_stereo_b24_4_swb_cbr_fer_ep_015_g192.192 out.wav

Crash happens in frame 830.

test_stereo_cut_stereo_b24_4_swb_cbr_fer_ep_015_g192.192