Web IDE: Fix the console error that happens when discarding a newly added/uploaded file.

What does this MR do?

Fix console error on discarding new files in Web IDE

In Web IDE, when you "discard all changes" for any newly added or uploaded file, an error occurs. This is because the Web IDE tries to close that file, but the closeFile action is called with the wrong type of parameter.

This partly fixes the problem in #27244 (closed), so we'd be one step closer to fixing the actual problem.

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