Fix: Check for empty playlists used the wrong tag

Use #EXTINF to check, if a playlist has entries instead of #EXT-X-STREAM-INF, which was accidentally used.
This tag only occurs in master playlists.

common/src/main/java/ctbrec/recorder/download/AbstractHlsDownload.java

@@ -67,7 +67,7 @@ public abstract class AbstractHlsDownload implements Download {
         try(Response response = client.execute(request)) {
             if(response.isSuccessful()) {
                 String body = response.body().string();
-                if(!body.contains("#EXT-X-STREAM-INF")) {
+                if(!body.contains("#EXTINF")) {
                     // no segments, empty playlist
                     return new SegmentPlaylist(segmentsURL);
                 }