upd

build/node/Operations/Structured.js

@@ -550,7 +550,11 @@ module.exports = function() {
     };
 
     ReplaceManager.prototype.deleteContent = function() {
+      var last_op;
+      last_op = this.getLastOperation();
+      if ((!last_op.isDeleted()) && last_op.type !== "Delimiter") {
         (new ops.Delete(null, void 0, this.getLastOperation().uid)).execute();
+      }
       return void 0;
     };
 

lib/Operations/Structured.coffee

@@ -507,6 +507,8 @@ module.exports = ()->
       @getLastOperation().isDeleted()
 
     deleteContent: ()->
+      last_op = @getLastOperation()
+      if (not last_op.isDeleted()) and last_op.type isnt "Delimiter"
         (new ops.Delete null, undefined, @getLastOperation().uid).execute()
       undefined