Better exception message when paths are not defined

[patrickkusebauch]

Currently:

$ php vendor/qossmic/deptrac/deptrac.php -vvv
collecting violations.

In Finder.php line 611:
                                                                                 
  [LogicException]                                                               
  You must call one of in() or append() methods before iterating over a Finder.  
                                                                                 

Exception trace:
  at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/symfony/finder/Finder.php:611
 Symfony\Component\Finder\Finder->getIterator() at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/qossmic/deptrac/src/InputCollector/FileInputCollector.php:62
 Qossmic\Deptrac\InputCollector\FileInputCollector->collect() at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/qossmic/deptrac/src/Analyser/AstMapExtractor.php:27
 Qossmic\Deptrac\Analyser\AstMapExtractor->extract() at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/qossmic/deptrac/src/Analyser/DependencyLayersAnalyser.php:44
 Qossmic\Deptrac\Analyser\DependencyLayersAnalyser->process() at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/qossmic/deptrac/src/Analyser/LegacyDependencyLayersAnalyser.php:24
 Qossmic\Deptrac\Analyser\LegacyDependencyLayersAnalyser->analyse() at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/qossmic/deptrac/src/Console/Command/AnalyseRunner.php:52
 Qossmic\Deptrac\Console\Command\AnalyseRunner->run() at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/qossmic/deptrac/src/Console/Command/AnalyseCommand.php:104
 Qossmic\Deptrac\Console\Command\AnalyseCommand->execute() at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/symfony/console/Command/Command.php:291
 Symfony\Component\Console\Command\Command->run() at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/symfony/console/Application.php:989
 Symfony\Component\Console\Application->doRunCommand() at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/symfony/console/Application.php:299
 Symfony\Component\Console\Application->doRun() at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/qossmic/deptrac/src/Console/Application.php:104
 Qossmic\Deptrac\Console\Application->doRun() at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/symfony/console/Application.php:171
 Symfony\Component\Console\Application->run() at /home/patrick/PhpstormProjects/deptrac-awesome/vendor/qossmic/deptrac/deptrac.php:27

analyse [-f|--formatter [FORMATTER]] [-o|--output [OUTPUT]] [--no-progress] [--fail-on-uncovered] [--report-uncovered] [--report-skipped] [--] [<depfile>]

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