On a producion SP2010 site I've workflow, created by a predecessor, which when opening in de workflow designer shows a red bar on top with the error "Error Object reference not set to an instance of an object":
Other workflows just open fine in de designer. Also notice that in this screenshot the workflow's version is missing. Which does show in the Workflow Inventory (it's 7.0).
Is it safe to save/publish it in order to resolve this? Or does it require some other solution?
Solved! Go to Solution.
Right, from the looks of it, the Object Reference error when opening a Nintex 2010 workflow (on-prem) in the designer seems to be caused by the account of the last publisher to be deleted. As i encountered another workflow last published by the same (deleted) user which open the editor with mentioned error, I was able to save a minor version with my account and then re-open the workflow without the error and publish it successfully.
For now I'll mark this post as the solution... If anyone has further insights, please feel free to share them with me.