[non-BE] Resolve "OMASA object editing path has wrong assignment"

• Related issues: #2496 (closed)
• Requested reviewers: @lintervo

Reason why this change is needed

• There is a porting error where assignment is done wrong.

Description of the change

• Fix the assignment.

Affected operating points

• Only decoder
• Probably non-BE for OMASA object editing cases when gain is not edited.

Closes #2496 (closed)