WorkflowTask version update on workflow page fails when there are Optional str

[jluethi]

Some of our tasks have optional str as input parameters. One of them is the Cellpose task. So far, they have not been an issue (and this manifest part has not changed on the task side), but something in the Fractal 1.0 update has changed how the updating goes.

Now, trying to update from 1 Cellpose version to another leads to the following issue:

/output_ROI_table: must be string

(for every optional str argument)

In the argument json, it is set as:

"output_ROI_table": null,

For example: