KNIME 4.1 java.lang.NullPointerException

I’ve created a new workflow for a client, but when trying to edit it I only get java.lang.NullPointerException message in the workflow. I’ve attached a copy of my .log file. This is a major issue since this is work that I’ve been doing and now, days worth of work seems to be gone.
Copy.log (384.2 KB)

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Hi @Willem,

Thanks for reporting this regression. The issue is related to empty / null flow variables of type String. We can reproduce it locally and will shortly provide a fix that should allow you to edit the workflow again. In the meantime, you should be able to open the workflow in KNIME Analytics Platfform 4.0.2 (albeit without the new nodes and functionality introduced in KNIME 4.1).

I’ll let you know as soon as the fix is available.

I’m deeply sorry for the inconvenience.




No worries.

I found that if I manually delete some of the loop nodes at specific places in my workflow I can edit it again. Luckily not too big of a workflow so I managed to get back into it.

Just some more information on this. Found that the “Table Row To Variable Loop Start” generates this scenario where it creates 2 empty variables.

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Thanks Marc,

I have a feeling that might explain some strange behaviour I’ve been seeing with one or two of the Vernalis test cases too.


Hi @Willem,

We have pushed a fix that should resolve the issue and let you open your workflows again. You’ll simply have to look for & install updates in your KNIME Analytics Platform 4.1.

Happy holidays,



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