Draft: Resolve "CLANG18 compiler warning with -O3: -Walloc-size-larger-than in ivas_vbap_fx.c"

• Related issues: #2288
• Requested reviewers: @pihlajakuja

Reason why this change is needed

• Compiler warning about variable (integer underflow) at compile time

Description of the change

• Added a safety check to ensure the malloc size is 0 or positive

Affected operating points

• N/A

Closes #2288