Link.php: refactore Link() to be reentrand.

extension/qfq/tests/phpunit/LinkTest.php

@@ -28,8 +28,21 @@ class LinkTest extends \PHPUnit_Framework_TestCase {
     public function testLinkSingle() {
         $link = new Link(null, $this->sip, true);
 
+        $result = $link->renderLink('');
+        $this->assertEquals($result, '');
+
+        $result = $link->renderLink('u');
+        $this->assertEquals($result, '');
+
+        $result = $link->renderLink('u:');
+        $this->assertEquals($result, '');
+
         $result = $link->renderLink('u:http://math.uzh.ch');
         $this->assertEquals($result, '<a href="http://math.uzh.ch" > </a>');
+
+        $result = $link->renderLink('u:http://math.uzh.ch|t:Hello world');
+        $this->assertEquals($result, '<a href="http://math.uzh.ch" >Hello World</a>');
+
     }
 
     public function testLinkClass() {