fix null link crash for music tracks

app/src/main/java/ru/vtosters/lite/music/M3UDownloader.java

@@ -1,5 +1,6 @@
 package ru.vtosters.lite.music;
 
+import android.util.Log;
 import com.vk.dto.music.MusicTrack;
 
 import java.io.File;
@@ -33,6 +34,12 @@ public class M3UDownloader implements ITrackDownloader {
     }
 
     public void downloadTrack(MusicTrack track, File outDir, Callback callback, boolean cache) {
+        if (track.D.isEmpty()) {
+            Log.d("TrackDownloader", "link error: " + track.y1() + ", title: " + M3UDownloader.getTitle(track));
+            callback.onFailure();
+            return;
+        }
+
         var request = new Request.a().b(track.D).a();
         try {
             var response = client.a(request).execute().a().g();
@@ -60,16 +67,7 @@ public class M3UDownloader implements ITrackDownloader {
         tsesDir.mkdirs();
         var resultTs = new File(tsesDir, "result.ts");
 
-        String title = null;
-
-        if (track.f != null) {
-            title = track.f;
-            if (!track.g.isEmpty()) {
-                title += " (" + track.g + ")";
-            }
-        }
-
-        var fileName = IOUtils.getValidFileName((cache ? "track" : track.C + " - " + title) + ".mp3");
+        var fileName = IOUtils.getValidFileName((cache ? "track" : track.C + " - " + getTitle(track)) + ".mp3");
         var resultMp3 = new File(outDir, fileName);
 
         callback.onProgress(5);
@@ -109,6 +107,19 @@ public class M3UDownloader implements ITrackDownloader {
         }).thenRun(() -> IOUtils.deleteRecursive(tsesDir)).thenRun(callback::onSuccess);
     }
 
+    public static String getTitle(MusicTrack track) {
+        String title = null;
+
+        if (track.f != null) {
+            title = track.f;
+            if (!track.g.isEmpty()) {
+                title += " (" + track.g + ")";
+            }
+        }
+
+        return title;
+    }
+
     // Initialization-on-demand
     private static class Holder {
         private static final M3UDownloader INSTANCE = new M3UDownloader();

app/src/main/java/ru/vtosters/lite/music/downloader/TrackDownloader.java

@@ -16,6 +16,12 @@ import ru.vtosters.lite.music.interfaces.ITrackDownloader;
 
 public class TrackDownloader {
     public static void downloadTrack(MusicTrack track, String path, Callback callback) {
+        if (track.D.isEmpty()) {
+            Log.d("TrackDownloader", "link error: " + track.y1() + ", title: " + M3UDownloader.getTitle(track));
+            callback.onFailure();
+            return;
+        }
+
         download(track, path, callback, M3UDownloader.getInstance(), false);
     }
 
@@ -23,6 +29,10 @@ public class TrackDownloader {
         if (CacheDatabaseDelegate.isCached(track.y1())) {
             callback.onSuccess();
             return;
+        } else if (track.D.isEmpty()) {
+            Log.d("TrackDownloader", "link error: " + track.y1() + ", title: " + M3UDownloader.getTitle(track));
+            callback.onFailure();
+            return;
         }
 
         var path = FileCacheImplementation.getTrackFolder(LibVKXClient.asId(track)).getAbsolutePath();