Harmonisation of modif_fs

• Related issues: #2410 (closed)
• Requested reviewers: @vaclav

Reason why this change is needed

• Most of modif_fs_fx and modif_fs_ivas_fx are the same, can easily be harmonized.

Description of the change

• Addition of 2 NULL parameters when he EVS versions is used.

Affected operating points

• Should be BE

  close #2410 (closed)