Fix regression bug in sandbox

lib/sandbox.js

@@ -176,7 +176,7 @@ function declare(path, timestamps, values) {
 function clear(path, timestamp, attributes) {
   state.uncommitted = true;
 
-  if (state.revision === maxRevision)
+  if (state.revision === state.maxRevision)
     state.clear.push([common.parsePath(path), timestamp, attributes]);
 }