Fix relative url in uploader URL

src/main/java/org/schabi/newpipe/extractor/services/youtube/YoutubeStreamInfoItemExtractor.java

@@ -94,13 +94,23 @@ public class YoutubeStreamInfoItemExtractor implements StreamInfoItemExtractor {
         }
     }
 
+    private static String fixRelativeUrls(String url) {
+        if(url == null || url.isEmpty()) return url;
+        if(url.startsWith("/")) {
+            return "https://youtube.com" + url;
+        } else {
+            return url;
+        }
+    }
+
     @Override
     public String getUploaderUrl() throws ParsingException {
         try {
             try {
-                return item.select("div[class=\"yt-lockup-byline\"]").first()
+                String url = item.select("div[class=\"yt-lockup-byline\"]").first()
                         .select("a").first()
                         .attr("href");
+                return fixRelativeUrls(url);
             } catch (Exception e){}
 
             // try this if the first didn't work