Crash when guides-cli is run without a configuration file

[greg0ire]

I thought I would test 0.3.0 on doctrine, and was greeted with this crash.

$ vendor/bin/guides -vvv --no-progress docs/en
PHP Fatal error:  Uncaught TypeError: is_file(): Argument #1 ($filename) must be of type string, bool given in /home/greg/dev/doctrine-orm/minor/vendor/phpdocumentor/guides-cli/bin/guides:44
Stack trace:
#0 /home/greg/dev/doctrine-orm/minor/vendor/phpdocumentor/guides-cli/bin/guides(44): is_file()
#1 /home/greg/dev/doctrine-orm/minor/vendor/bin/guides(119): include('...')
#2 {main}
  thrown in /home/greg/dev/doctrine-orm/minor/vendor/phpdocumentor/guides-cli/bin/guides on line 44

I believe it's caused by #768 (realpath returns false, and then false is passed to is_dir)

[wouterj]

Hmm, indeed. We should move $projectConfig = realpath($projectConfig); in the if statement