finishing for tutorial

lib/ConnectorAdapter.coffee

@@ -46,5 +46,7 @@ adaptConnector = (connector, engine, HB, execution_listener)->
     if op.uid.creator isnt HB.getUserId()
       engine.applyOp op
 
+  if connector._whenBoundToYatta?
+    connector._whenBoundToYatta()
 
 module.exports = adaptConnector

lib/Types/JsonTypes.coffee

@@ -175,7 +175,7 @@ module.exports = (HB)->
     # Whether the default is 'mutable' (true) or 'immutable' (false)
     #
     mutable_default:
-      true
+      false
 
     #
     # Set if the default is 'mutable' or 'immutable'

lib/yatta-element.coffee

@@ -53,7 +53,7 @@ Polymer "yatta-property",
         # since it is more safe (consider someone putting a custom Object type here)
       else if @val.type is "JsonType"
         bindToChildren @
-      else if @val isnt @parentElement.val.val(@name)
+      else if @parentElement.val?.val? and @val isnt @parentElement.val.val(@name)
         @parentElement.val.val @name, @val