Fix default arguments

Author: sebastianbergmann

src/Chunk.php

@@ -60,7 +60,7 @@ class Chunk
     private $endRange;
     private $lines;
 
-    public function __construct($start = null, $startRange = 1, $end = null, $endRange = 1, array $lines = array())
+    public function __construct($start = 0, $startRange = 1, $end = 0, $endRange = 1, array $lines = array())
     {
         $this->start      = (int) $start;
         $this->startRange = (int) $startRange;