lektor: Admin broken on master

I get this on master:

Uncaught (in promise) TypeError: Cannot read property 'props' of undefined
    at Object.isActive (http://localhost:5000/admin/static/gen/app.js:9182:27)
    at http://localhost:5000/admin/static/gen/app.js:9241:29
    at Array.map (native)
    at Object.render (http://localhost:5000/admin/static/gen/app.js:9232:44)
    at http://localhost:5000/admin/static/gen/vendor.js:16301:22
    at measureLifeCyclePerf (http://localhost:5000/admin/static/gen/vendor.js:15581:13)
    at ReactCompositeComponentWrapper._renderValidatedComponentWithoutOwnerOrContext (http://localhost:5000/admin/static/gen/vendor.js:16300:26)
    at ReactCompositeComponentWrapper._renderValidatedComponent (http://localhost:5000/admin/static/gen/vendor.js:16327:33)
    at ReactCompositeComponentWrapper.performInitialMount (http://localhost:5000/admin/static/gen/vendor.js:15867:31)
    at ReactCompositeComponentWrapper.mountComponent (http://localhost:5000/admin/static/gen/vendor.js:15763:22)

Oddly enough the generated code seems completely wrong:

	  isActive: function isActive(field) {
	    var value = undefined.props.value;
	    if (value == null) {
	      value = undefined.props.placeholder;
	      if (value == null) {
	        return false;
	      }
	    }

Not sure why this is undefined.props; the source says this.props.