Resolve sanitizer error in object editing in OMASA

• Related issues: #1217 (closed)
• Requested reviewers: @paulusj, @weckbecker

Reason why this change is needed

• Object editing is not tested for the moment.

Description of the change

• fix sanitizer error (uninitialized value): do object editing only when object metadata is available
• replace hIvasDec->st_ivas by st_ivas

Affected operating points

• All is BE for the current self-test.