How can I set "default value" to blank?

I need set some string field’s defalut value to “”, but I can’t set it via admin tool. So I add "default": "" line to model.setting.json manually like this:

"name": {
  "type": "string",
  "default": ""

But if I edit model.setting.json(such as add a new field, or adjust some field setting). then the "default": "" was removed from model.setting.json. My question is can I keep "default": "" in setting.json file?

System Information
  • Strapi Version: 3.6.2
  • Operating System: macOS Big Sur
  • Database: MongoDB 4.0.14
  • Node Version: v12.19.0
  • NPM Version: 6.4.1
  • Yarn Version:

Looks like all field types will lost the "default" : "" when save model via admin tool. May I know how to keep it when saving?