Resolve "[CLANG18] MSAN: use-of-uninitialized-value in lib_dec/ivas_core_dec.c:333:24"

• Related issues: #1481 (closed)
• Requested reviewers:

Reason why this change is needed

• Fix MSAN complaint in CLANG18

Description of the change

• Initialize last_element_brate in SCE upon struct creation - same as done for CPE already. Value is passed to a function, but not actually used inside, so no functional changes expected.

Affected operating points

• None

Related to #1481 (closed)