[#49] Ensure a URI instance is always present

- If none is provided, lazy-instantiate one.

Author: weierophinney

src/RequestTrait.php

@@ -98,7 +98,7 @@ private function initialize($uri = null, $method = null, $body = 'php://memory',
         }
 
         $this->method = $method ?: '';
-        $this->uri    = $uri;
+        $this->uri    = $uri ?: new Uri();
         $this->stream = ($body instanceof StreamInterface) ? $body : new Stream($body, 'r');
 
         list($this->headerNames, $headers) = $this->filterHeaders($headers);