Track.Id must now always be valid (if present).

src/main/java/de/dennisguse/opentracks/content/data/Track.java

@@ -26,7 +26,6 @@ import java.util.Objects;
 import java.util.UUID;
 
 import de.dennisguse.opentracks.stats.TrackStatistics;
-import de.dennisguse.opentracks.util.PreferencesUtils;
 
 /**
  * A track.
@@ -127,11 +126,6 @@ public class Track {
             return id;
         }
 
-        @Deprecated //TODO Use a Track.Id of null instead
-        public boolean isValid() {
-            return id != PreferencesUtils.RECORDING_TRACK_ID_DEFAULT;
-        }
-
         @Override
         public boolean equals(Object o) {
             if (this == o) return true;