Avoid rendering of private CSS properties

src/domain_abstract/model/Styleable.js

@@ -97,7 +97,8 @@ export default {
       const imp = opts.important;
       const important = isArray(imp) ? imp.indexOf(prop) >= 0 : imp;
       const value = `${style[prop]}${important ? ' !important' : ''}`;
-      value && result.push(`${prop}:${value};`);
+      const propPrv = prop.substr(0, 2) == '__';
+      value && !propPrv && result.push(`${prop}:${value};`);
     }
 
     return result.join('');