Fix [MSAN Clang 18] use-of-uninitialized-value in stereo_tcx_core_enc

• Related issues: #1384
• Requested reviewers: @multrus

Reason why this change is needed

• MSAN Clang 18 reportes use-of-uninitialized-value in stereo_tcx_core_enc().

Description of the change

• Fix MSAN Clang 18 error on use-of-uninitialized-value in stereo_tcx_core_enc().

Affected operating points

• All is BE.

Related to #1384