Msan error in MC param upmix encoder for WB
### Basic info
- Commit SHA: ca227f6e591a609d40ef8d2e597a4a26746ef73a
### Bug description
Clang msan sanitizer test in pipeline found an error:
<!--- Copy sanitizer traceback from command line here -->
```
==2431==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x5f5e44 in ivas_mc_paramupmix_param_est_enc /builds/rep/ivas-codec-pc/ivas-codec/lib_enc/ivas_mc_paramupmix_enc.c:839:28
#1 0x5f2ac0 in ivas_mc_paramupmix_enc /builds/rep/ivas-codec-pc/ivas-codec/lib_enc/ivas_mc_paramupmix_enc.c:101:5
#2 0x57129c in ivas_enc /builds/rep/ivas-codec-pc/ivas-codec/lib_enc/ivas_enc.c:315:13
#3 0x4c190c in IVAS_ENC_EncodeFrameToSerial /builds/rep/ivas-codec-pc/ivas-codec/lib_enc/lib_enc.c:1153:24
#4 0x4a6b55 in main /builds/rep/ivas-codec-pc/ivas-codec/apps/encoder.c:743:24
#5 0x7f9292efed8f in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#6 0x7f9292efee3f in __libc_start_main csu/../csu/libc-start.c:392:3
#7 0x421514 in _start (/builds/rep/ivas-codec-pc/ivas-codec/CLANG1/IVAS_cod+0x421514)
SUMMARY: MemorySanitizer: use-of-uninitialized-value /builds/rep/ivas-codec-pc/ivas-codec/lib_enc/ivas_mc_paramupmix_enc.c:839:28 in ivas_mc_paramupmix_param_est_enc
Exiting
```
<!--- Copy test job URL here -->
Link to test pipeline: https://forge.3gpp.org/rep/ivas-codec-pc/ivas-codec/-/jobs/84633
### 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 -->
```
python3 scripts/IvasBuildAndRunChecks.py --checks CLANG1 -m MC_7_1_4_b160_wb_cbr -p /path/to/my/local/ci_linux_ltv_local.json
```
or directly:
```
make clean
make -j CLANG=1
# resample ltv48_MC714.wav to 16kHz...
./IVAS_cod -mc 7_1_4 -max_band wb 160000 16 ltv48_MC714_16k.wav bit
```
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issue