fix broken vignette

assign correct type for new entity objects

Author: grlloyd

doc/struct_model.Rmd

@@ -298,7 +298,7 @@ model_template=setClass('model_template', # replace model_template with ...
         
         # entities can be initialised with populated slots
         outputs.result_1=entity(name='Result 1',type='dataset',
-            description='An example entity object'),
+            description='An example entity object',value=dataset()),
         
         # outputs dont have to be entity objects but we dont recommend this.
         outputs.result_2=2