Fix benign log "Bugsnag.notify() was called before Bugsnag.start()"

[deepakprabhakara]

What steps did you take and what happened:

When Bugsnag is not setup notify complains that start was never called. notify should become a no-op when start is not called. This is a completely harmless log that is being displayed now but it's better to abstract error notification and include Bugsnag as one of the providers.

What did you expect to happen:

Any relevant output that will help us better understand what's going on:

(Pasting long output into a GitHub gist or other pastebin is fine.)

Anything else you would like to add:

[Miscellaneous information that will assist in solving the issue.]

Environment:

• Retraced version:
• SDK: