Avoid problems in toolbar startup.

The correct thing to do is detect when the exception might happen and avoid
it, not try to catch it.
Add a toggle for the parachute warning.

It defaults to on since this is a useful feature for people new to DRE,
but it is most annoying for veterans.
Plug an NRE hole.

And remove the superfluous try/catch block. Having the correct Event
name helps.
Fix a typo.

s/unsave/unsafe/
Remove an unnecessary null check.

If OnSave is called, Instance cannot be null because it is guaranteed that
Awake will have been called.
Move the chute warning flag to the scenario.

This makes the setting "global" (ie for all difficulty settings) and
actually save properly without needing to hack the config files. It also
has the effect of making the setting per-save, which I consider to be a
good thing as it will serve as a reminder.
Visually separate the chute toggle from the other settings.

This makes it clear that the chute warning toggle is not part of the
difficulty settings.
Merge pull request #5 from taniwha-qf/master

NRE fixes and chute warning toggle.