GREG-60: Setting default value to blank, not undefined, to avoid warning

frontend/src/routes/register/index.tsx

@@ -134,7 +134,7 @@ export default function Register() {
                             <Select
                               labelId='roletype-select-label'
                               id='roletype-select'
-                              defaultValue={undefined}
+                              defaultValue=''
                               error={!!errors.role_type}
                               label={t('input.roleType')}
                               onChange={(role) => {