minor phpdoc fixes

Author: Tobion

src/MessageTrait.php

@@ -17,7 +17,7 @@ trait MessageTrait
     /** @var string */
     private $protocol = '1.1';
 
-    /** @var StreamInterface */
+    /** @var StreamInterface|null */
     private $stream;
 
     public function getProtocolVersion()

src/functions.php

@@ -439,7 +439,7 @@ function hash(
  * Read a line from the stream up to the maximum allowed buffer length
  *
  * @param StreamInterface $stream    Stream to read from
- * @param int             $maxLength Maximum buffer length
+ * @param int|null        $maxLength Maximum buffer length
  *
  * @return string
  */