Workflow fails when run from command line with error ***WARNING: Display must be created on main thread due to Cocoa restrictions. Use vmarg -XstartOnFirstThread

I’ve been running a workflow successfully using version 4.5.2 on MacOS every evening. Since adding BarChart nodes, to replace JFreeChart Pie Charts, The workflow will not run unattended.

The error message

***WARNING: Display must be created on main thread due to Cocoa restrictions. Use vmarg -XstartOnFirstThread

seems to suggest that the nodes are trying to open the interactive charts; I only need to create images from these nodes, to display on a website.

Is it possible to use these nodes in a workflow from the command line? Can I suppress the automatic opening of the charts, if this is indeed the problem.

Andy