Merge pull request TeamNewPipe#1200 from TeamNewPipe/bandcamp-fix-null-url-catenation

[Bandcamp] Null-safe url catenation in track playlist

Author: TobiGr

extractor/src/main/java/org/schabi/newpipe/extractor/services/bandcamp/extractors/streaminfoitem/BandcampPlaylistStreamInfoItemExtractor.java

@@ -43,7 +43,12 @@ public String getName() {
 
     @Override
     public String getUrl() {
-        return getUploaderUrl() + track.getString("title_link");
+        final String relativeUrl = track.getString("title_link");
+        if (relativeUrl != null) {
+            return getUploaderUrl() + relativeUrl;
+        } else {
+            return null;
+        }
     }
 
     @Override
@@ -66,7 +71,7 @@ public String getUploaderName() {
     @Nonnull
     @Override
     public List<Image> getThumbnails() throws ParsingException {
-        if (substituteCovers.isEmpty()) {
+        if (substituteCovers.isEmpty() && getUrl() != null) {
             try {
                 final StreamExtractor extractor = service.getStreamExtractor(getUrl());
                 extractor.fetchPage();