Error executing code: FormRun (data source) has no valid runable code in method 'new' when trying to edit Project workflow

If you go to Project management and accounting > Setup > Project Management and accounting workflow and you select any workflow and hit Edit and you get an error stating

"Error executing code: FormRun (datasource) hasnovalid runnable codeinmethod 'new'

Try to to locate the form that is failing to launch in the AOT. In this case it will be 'WorkFlowEditorHost'. Make a small change to the form, compile it and then delete the change and recompile.

Try now to see if you are able to edit the workflow after this.