Resolves selahattinunlu#52: URI Parser.

- Changed return value from null to empty string in `UriParser::setQueryUri` method, if query params were not pass. It needs, so that `Paginator::setQueryUri` str_replace get empty string instead of `null` and does not crash.

src/UriParser.php

@@ -80,7 +80,7 @@ private function setQueryUri($uri)
     {
         $explode = explode('?', $uri);
 
-        $this->queryUri = (isset($explode[1])) ? rawurldecode($explode[1]) : null;
+        $this->queryUri = (isset($explode[1])) ? rawurldecode($explode[1]) : '';
     }
 
     private function setQueryParameters($queryUri)