core:schema:warn Unknown property 0 for component/system

[ChristopheBougere]

Quite similar to #40
When creating a custom component which has no properties, React converts this:
<Entity my-custom-component />
to
<Entity my-custom-component="true" />
Aframe is expecting an object for the schema, and thinks it has 4 properties (t, r, u and e).
A quick workaround is to set an empty string as property:
<Entity my-custom-component="" />
But could this be fixed by aframe-react?