Don't crash if on write-protected disk

[seritools]

If TOPBENCH is on a write-protected floppy, it exits with a rather non-descriptive Runtime error 150.

Ideally it'd still work (without the ability to write to the database, of course)

[MobyGamer]

Ah, I see it tries to write TOPBENCH.LOG no matter what. I'll see about fixing or working around this.