This only affected PRS1, and it seems like the other places where
the broken Session::hours() result was used were:
- GT_SESSIONS, which seems to be unused
- settings_wavg, where it had no effect
The other uses of Settings::hours() were where there was only
a single slice, in which case it returned the right result:
- gSessionTimesChar::paint (the one still in use)
- Icon loader
- Resmed loader
Remarkably, this resulted in nearly no changes to the test output.
Only one session with 0 duration had its start/end times reset to 0,
since it will no longer get imported.
