Print message when no models are loaded;

examples/Interaction/Controller_Models/main.lua

@@ -3,6 +3,8 @@ function lovr.load()
     left = lovr.headset.newModel('hand/left'),
     right = lovr.headset.newModel('hand/right')
   }
+
+  if not next(models) then print('No models loaded') end
 end
 
 function lovr.draw()