[feature request] Select selector allow create to create an empty entry

### Existing Component
是

### Component Name
Select 选择器

### Description
Select 选择器 allow-create 可以创建空条目,建议增加属性配置是否可以增加空条目或不允许创建空条目

Start at the Select component's existing allow-create behavior and inspect how empty entries are currently handled. Define the configuration's expected behavior from the issue, then verify that it distinguishes allowing an empty created entry from rejecting it; the payload names no source file or test.

Written by the indexing model from the issue text.