message: Fix level select should clear further down levels, hide select when only one choice.
diff: @@ -436,15 +436,18 @@ const RequestAudit: FC<RequestAuditProps> = ({ roles, signedInAddress }) => {
  </> : <>
  <h3 id="lookupForm">Choose an emissions factor</h3>
  {level1sQuery.data &&
  - <FormSelectRow form={emForm} setForm={setEmForm} errors={formErrors} field="level_1" label="Level 1" values={level1sQuery.data.emissionsFactors}/>
  + <FormSelectRow form={emForm} setForm={setEmForm} errors={formErrors} field="level_1" label="Level 1" values={level1sQuery.data.emissionsFactors}
  + onChange={(val)=>{setEmForm({...emForm, level_1:val, level_2:'', level_3: '', level_4: ''})}}/>
  }
  {emForm.level_1 && level2sQuery.data &&
  - <FormSelectRow form={emForm} setForm={setEmForm} errors={formErrors} field="level_2" label="Level 2" values={level2sQuery.data.emissionsFactors}/>
  + <FormSelectRow form={emForm} setForm={setEmForm} errors={formErrors} field="level_2" label="Level 2" values={level2sQuery.data.emissionsFactors}
  + onChange={(val)=>{setEmForm({...emForm, level_2:val, level_3: '', level_4: ''})}}/>
  }
  {emForm.level_1 && emForm.level_2 && level3sQuery.data &&
  - <FormSelectRow form={emForm} setForm={setEmForm} errors={formErrors} field="level_3" label="Level 3" values={level3sQuery.data.emissionsFactors}/>
  + <FormSelectRow form={emForm} setForm={setEmForm} errors={formErrors} field="level_3" label="Level 3" values={level3sQuery.data.emissionsFactors}
  + onChange={(val)=>{setEmForm({...emForm, level_3:val, level_4: ''})}}/>
  }
  - {emForm.level_1 && emForm.level_2 && emForm.level_3 && level4sQuery.data &&
  + {emForm.level_1 && emForm.level_2 && emForm.level_3 && level4sQuery.data && level4sQuery.data.emissionsFactors.length > 1 &&
  <FormSelectRow form={emForm} setForm={setEmForm} errors={formErrors} field="level_4" label="Level 4" values={level4sQuery.data.emissionsFactors}/>
  }
  {lookupQuery.data ?
  