Fixed a bug when phplint is active and only non-php files are commited

There was a bug when you try to commit (pre-hook) some non-php files.
You receive the PHP Parallel Lint usage error every time. With this it
will be marked as "skipped" when no files are available to pass trough
the linter.

Author: glamorous

src/Task/PhpLint.php

@@ -53,6 +53,10 @@ public function run(ContextInterface $context): TaskResultInterface
             ->notPaths($config['ignore_patterns'])
             ->extensions($config['triggered_by']);
 
+        if ($files->isEmpty()) {
+            return TaskResult::createSkipped($this, $context);
+        }
+
         $arguments = $this->processBuilder->createArgumentsForCommand('parallel-lint');
         $arguments->add('--no-colors');
         $arguments->addOptionalArgumentWithSeparatedValue('-j', $config['jobs']);