Empty .svg worfklow file, if workflow saved without changes

[gerlingsm]

Describe the bug If an existing workflow is opened for editing via Kitodo and then saved again without making any changes to it, the corresponding workflow .svg will end up being 0 bytes in size and therefore empty/broken. This only affects the svg image file, the workflow itself remains unchanged. (The file is only rewritten, which can be recognised by the modification date of the file)

To Reproduce Steps to reproduce the behavior:

1. Go to 'Project' --> 'Workflows'
2. Open an existing workflow
3. Do NOT make any changes to the workflow and save it
4. Workflow is saved without an error message
5. Determine that the associated .svg file is empty / 0 bytes in size
6. 1. Apart from the filesystem, you will also notice this in the corresponding process template when you unfold it

Expected behavior Saving workflow without changes should also result in a functioning .svg file

Workaround

1. Open the Workflow
2. CHANGE anything in the workflow (for example remove and readd "end")
3. Save the workflow
4. A new correct svg file should be generated

Screenshots

Release Tested with 3.7.1

Desktop (please complete the following information):

• OS: Kubuntu 22.04
• Browser Firefox
• Version 132.0 (64-bit)