Sort Directory doesn't order SYS files with ".SYSTEM" suffix

[inexorabletash]

Describe the bug
If sorting w/o selection, the Sort Directory DA sorts SYS files with ".SYSTEM" suffix before all other files, but doesn't compare them against each other.

To Reproduce
Steps to reproduce the behavior:

1. Start DeskTop
2. Copy BASIC.SYSTEM to an empty dir (e.g. a RAM Disk)
3. Duplicate BASIC.SYSTEM to A.SYSTEM
4. Duplicate BASIC.SYSTEM to C.SYSTEM
5. Clear selection
6. Apple Menu > Sort Directory

Expected behavior

A.SYSTEM, BASIC.SYSTEM, C.SYSTEM

Actual behavior

BASIC.SYSTEM, A.SYSTEM, C.SYSTEM

Additional context
Add any other context about the problem here.

Not new in 1.3. This behavior is present in 1.2 (and probably 1.1)