af_redditimgur: absolutize links before working on them

plugins/af_redditimgur/init.php

@@ -651,7 +651,9 @@ class Af_RedditImgur extends Plugin {
 				$xpath = new DOMXPath($doc);
 
 				/** @var ?DOMElement $content_link */
-				$content_link = $xpath->query("(//a[contains(., '[link]')])")->item(0);
+				$content_link = UrlHelper::rewrite_relative($article["link"],
+					$xpath->query("(//a[contains(., '[link]')])")->item(0),
+						"a");
 
 				if ($this->host->get($this, "enable_content_dupcheck")) {