Go back to home screen when close puzzle file explore

[DavidColetta]

Description

When you open the file explorer, and either do not select any file, or select a file that cannot be opened, you are not sent back to the home screen.

Closes #307

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Enhancement (improvement to an already existing feature)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

Try opening a puzzle, either to solve or to edit. If it is a valid file, it opens as normal. However, if you press cancel, or select an invalid file, you will find yourself sent back to the homescreen.

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[Corppet]

Changes look good, however, in the future please carefully review the checklist and make sure you ONLY check the actions done under that list. I don't see any new tests added, so the respective action item is not checked (it doesn't mean that this PR is incomplete, but helps maintain the accuracy of the details of the changes).