Boolean field with feel required breaks the editor

[marstamm]

Describe the Bug

Adding the property

      {
        "label": "Demo",
        "value": false,
        "type": "Boolean",
        "feel": "required",
        "binding": {
          "type": "zeebe:input",
          "name": "foo"
        }
      }

will break the feel editor

Steps to Reproduce

1. add the property to template
2. apply template
3. Try to edit field. It is broken

Expected Behavior

The FEEL editor shows =false and is editable

Additional info

Reported here: camunda/camunda-modeler#4154 (comment)
related to camunda/camunda-modeler#3622

Environment

• Host (Browser/Node version), if applicable: [e.g. MS Edge 18, Chrome 69, Node 10 LTS]
• OS: [e.g. Windows 7]
• Library version: [e.g. 2.0.0]