fix: '..' shouldn't be ignored if directories is empty

[ArrayZoneYour]

What:

append .. to directories if directories is empty

Why:

pathDiff will broken if url startsWith ..

AbstractFileManager.prototype.pathDiff('../assets/', '') returns assets/ now

How:

pop directories only if it is not empty

Checklist:

• [ ] Documentation
• [ ] Added/updated unit tests
• [x] Code complete