Fix callback calls. See mikeric#650. Regression since mikeric#546

src/adapter.coffee

@@ -77,7 +77,7 @@ Rivets.public.adapters['.'] =
                 callbacks = map.callbacks
 
                 if callbacks[keypath]
-                  cb() for cb in callbacks[keypath]
+                  cb() for cb in callbacks[keypath].slice() when cb in callbacks[keypath]
                 @observeMutations newValue, obj[@id], keypath
 
     unless callback in callbacks[keypath]