Unsaved Empty Inputs in Volunteer Profile

### Description

Changes to optional inputs are not saved in the Volunteer Profile if they are left empty.

### Steps to Reproduce

1. Go to the 'Lista Voluntari' page.
2. Select a volunteer and open their profile.
3. Click the 'Editeaza' button.
4. Clear the inputs for branch, department, and role.
5. Click the 'Salveaza Modificari' button.

### Expected Result

5. The changes should be saved.

### Actual Result
5. No changes are saved; the data remains unchanged.

### Notes

The payload does not include the empty inputs.