Fixed error in MainPresenter

- Pretty dumb mistake, didn't put a reference to mMainView within the
if statement that checks if it isn't null
2 jobs for master in 3 minutes and 8 seconds (queued for 2 seconds)
Name Stage Failure
failed
build Build There is an unknown failure, please try again
> Crashlytics Developer Tools error.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Total time: 49.42 secs
ERROR: Job failed: exit code 1