[non-BE] Resolve "Porting error in ivas_merge_masa_metadata_fx"

• Related issues: #2525 (closed)
• Requested reviewers: @vasilache

Reason why this change is needed

• There is a wrong assignment

Description of the change

• Fix the assignment

Affected operating points

• Encoder non-BE
• Lower bitrates of OMASA can be affected

Closes #2525 (closed)