Update bin/quickdump.php

Co-authored-by: Oliver Klee <github@oliverklee.de>

Author: SjorsO

bin/quickdump.php

@@ -12,7 +12,7 @@
 require_once(__DIR__ . '/../vendor/autoload.php');
 
 $source = \file_get_contents('php://stdin');
-if ($source === false) {
+if (!\is_string($source)) {
     throw new \RuntimeException('Failed to read from stdin.');
 }
 $parser = new Parser($source);