Fix create snippet disabled on empty file path

What does this MR do?

This MR fixes #239341 (closed) introduced in !38855 (merged).

It turns out that the BE supports sending empty file paths for snippets, and a file name will be auto-generated.

Screenshots

Before	After	After submission

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

References

• Related to #239341 (closed)