Fix Content View access when the Schemas registry contains "long" property

Steps to reproduce

1. add some code to the Schemas registry like

   {
     "schemas": {
       
       "blabla": {
         "foo": "string",
         "bar": "long"
       }
     }
     
   }
   

2. navigate to a content view
3. observe a popup with an error like

   (TypeError) : ZMb(...) is undefined
   Uncaught exception: com.google.gwt.core.client.JavaScriptException: (TypeError) : ZMb(...) is undefined