Nullpointerexception in ComputationGraph.outputOfLayersDetached

[cyberbeat]

I have a network with:

EmbeddingSequenceLayer
LastTimeStepVertex
LossLayer

and defined both, LastTimeStepVertex and LossLayer as output (for debugging purposes).

Training works, but inference throws an exception:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "org.deeplearning4j.nn.workspace.LayerWorkspaceMgr.setHelperWorkspacePointers(java.util.Map)" because "workspaceMgr" is null
	at org.deeplearning4j.nn.graph.ComputationGraph.outputOfLayersDetached(ComputationGraph.java:2335)
	at org.deeplearning4j.nn.graph.ComputationGraph.output(ComputationGraph.java:1882)
...

In ComputationGraph.outputOfLayersDetached this code in line 2322 seems risky:

                if (closeAtEndIteraton[i] != null) {
                    for (MemoryWorkspace wsAct : closeAtEndIteraton[i]) {
                        wsAct.close();
                        LayerWorkspaceMgr canNowReuse = openActivationsWorkspaces.remove(wsAct);
                        freeWorkspaceManagers.add(canNowReuse);
                    }
                }

canNowReuse may be null - and is in my case, I tested with a if ..!=null statement before freeWorkspaceManagers.add(canNowReuse);