misc: add warning if on delete

Add a small toast when the user clicks the delete
action, but no settings haven't added yet.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>
aero: fix potential OutOfBounds exception

Signed-off-by: Blechd0se <alex.christ@hotmail.de>
aero: replace strings with constants

Signed-off-by: Blechd0se <alex.christ@hotmail.de>
statistics: fix number format exception

If because of whatever reason we can't find any
valid cpu time data, dont crash.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>
aero: add back-button logic back again

After two taps on the back button the app will quit.
Re-implemented since many users liked it that way.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>