USAN: index out of bounds in MC bitrate switching for decoding to STEREO
### Basic info
- Commit SHA: c3148745db6f787b2bee5b1eaca0b2ae5393c305
### Bug description
Clang usan sanitizer test in pipeline found an error:
<!--- Copy sanitizer traceback from command line here -->
```
lib_dec/ivas_jbm_dec.c:2588:28: runtime error: index 8 out of bounds for type 'int16_t [8]'
SUMMARY: UndefinedBehaviorSanitizer: out-of-bounds-index lib_dec/ivas_jbm_dec.c:2588:28 in
```
<!--- Copy test job URL here -->
Link to test pipeline: https://forge.3gpp.org/rep/ivas-codec-pc/ivas-codec/-/jobs/218857
### Ways to reproduce
Using the [scripts](https://forge.3gpp.org/rep/ivas-codec-pc/ivas-codec/-/wikis/Software-development/pyivastest-howto#how-to-reproduce-tests):
<!--- check correct sanitizer type -->
<!--- add error pattern if needed -->
[dly_profile.dat](/uploads/7acaa201ac7e1285bd7e707c41afb140/dly_profile_2_.dat)
```
python3 scripts/IvasBuildAndRunChecks.py --checks CLANG3 -m MC_5_1_ball_fb_rs -p /path/to/my/local/ci_linux_ltv_local.json --usan_supp_file scripts/ubsan.supp -J dly_profile.dat
```
or directly:
```
make clean
make -j CLANG=3
./IVAS_cod -mc 5_1 -max_band fb scripts/switchPaths/sw_13k2_512k.bin 48 ltv48_MC51.wav bit
networkSimulator_g192 dly_profile.dat bit bit_jbm_fer
./IVAS_dec -VOIP stereo 48 bit_jbm_fer out.wav
```
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issue