Restored test

Author: litetex

extractor/src/test/java/org/schabi/newpipe/extractor/services/youtube/YoutubeMixPlaylistExtractorTest.java

@@ -296,6 +296,16 @@ public static void setUp() throws IOException {
             dummyCookie.put(YoutubeMixPlaylistExtractor.COOKIE_NAME, "whatever");
         }
 
+        @Test
+        void getPageEmptyUrl() throws Exception {
+            extractor = (YoutubeMixPlaylistExtractor) YouTube
+                    .getPlaylistExtractor("https://www.youtube.com/watch?v=" + VIDEO_ID
+                            + "&list=RD" + VIDEO_ID);
+
+            extractor.fetchPage();
+            assertThrows(IllegalArgumentException.class, () -> extractor.getPage(new Page("")));
+        }
+
         @Test
         void invalidVideoId() throws Exception {
             extractor = (YoutubeMixPlaylistExtractor) YouTube