Filenames with whitespaces lead to error during export

[solth]

Describe the bug If filenames of images contain whitespaces, this leads to an error during export. Related to #5044

To Reproduce Steps to reproduce the behavior:

1. Create a process
2. Add images whose filenames contain whitespaces
3. Try to export the process
4. See error in the task manager

Expected behavior Whitespace in filename should not lead to errors during export

Release 3.7.0-SNAPSHOT (current master)

Additional context The same error has been fixed for uploading image files using the context menu in the metadata editor in #5622, so perhaps a solution for this bug can take the same approach used there.