Return error code 1 if no email has been found

This really small change makes your script return with error code 1 if no email could be found. This allows this command to easily be used along with other scripts:

```bash
$ bash findGitHubEmail clue || echo Nothing found
christian@lueck.tv
$ bash findGitHubEmail osudhgdsfgheuiorh || echo Nothing found
Nothing found
```