Fix dokufreaks#111 external images in links were broken

This fixes the fix for internal relatively referenced images such that
it is really only applied to internal images and not external images.

_test/media_linktitle_conversion.test.php

@@ -19,6 +19,7 @@ public function setUp() {
   * [[test|{{dokuwiki.png}}]]
   * [[#test|{{dokuwiki.png?w=200}}]]
   * [[doku>test|{{dokuwiki.png?w=300}}]]
+  * [[test|{{https://www.dokuwiki.org/lib/tpl/dokuwiki/images/logo.png}}]]
 EOF
             , 'Test setup');
         idx_addPage('wiki:included');
@@ -41,4 +42,9 @@ public function testInterWikiLinkTitleConversion() {
         $html = p_wiki_xhtml('test:include');
         $this->assertContains('src="'.ml('wiki:dokuwiki.png', array('w' => '300')).'"', $html);
     }
+
+    public function testExternalMediaNotConverted() {
+        $html = p_wiki_xhtml('test:include');
+        $this->assertContains('src="'.ml('https://www.dokuwiki.org/lib/tpl/dokuwiki/images/logo.png').'"', $html);
+    }
 }

helper.php

@@ -308,7 +308,7 @@ function _convert_instructions(&$ins, $lvl, $page, $sect, $flags, $root_id, $inc
 
         for($i=0; $i<$num; $i++) {
             // adjust links with image titles
-            if (strpos($ins[$i][0], 'link') !== false && isset($ins[$i][1][1]) && is_array($ins[$i][1][1])) {
+            if (strpos($ins[$i][0], 'link') !== false && isset($ins[$i][1][1]) && is_array($ins[$i][1][1]) && $ins[$i][1][1]['type'] == 'internalmedia') {
                 // resolve relative ids, but without cleaning in order to preserve the name
                 $media_id = resolve_id($ns, $ins[$i][1][1]['src']);
                 // make sure that after resolving the link again it will be the same link