Handle eof in line switches

[ajafff]

PR checklist

• Addresses an existing issue: tslint-switch disable-next-line throws when next line ends with EOF #1899
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

What changes did you make?

To get the end of the next-line switch, tslint searches for the start of the line after the next line. If there is no such line, tslint crashed.
This change checks, if the line in question exists. You can now use the next-line switch without even having a next line (which doesn't make sense at first glance, but is useful when linting live during development)

Is there anything you'd like reviewers to focus on?

(optional)

[nchen63]

can you turn on CircleCI?

[nchen63]

@ajafff thanks!