Store sensor data without distance.

Fixes #1088.

src/main/java/de/dennisguse/opentracks/data/models/TrackPoint.java

@@ -56,7 +56,7 @@ public class TrackPoint {
 
         SEGMENT_START_AUTOMATIC(-1), //Start of a segment due to too much distance from previous TrackPoint
         TRACKPOINT(0), //Just GPS data and may contain BLE sensor data
-        SENSORPOINT(2), //Just BLE sensor data; required to have speed and sensorDistance
+        SENSORPOINT(2), //Just BLE sensor data; may have speed and sensorDistance
 
         SEGMENT_END_MANUAL(1); //End of a segment
 

src/main/java/de/dennisguse/opentracks/services/TrackRecordingManager.java

@@ -10,6 +10,7 @@ import android.util.Pair;
 
 import androidx.annotation.NonNull;
 
+import java.time.Duration;
 import java.time.ZoneOffset;
 
 import de.dennisguse.opentracks.R;
@@ -180,8 +181,16 @@ class TrackRecordingManager implements SharedPreferences.OnSharedPreferenceChang
         }
 
         if (!trackPoint.hasLocation() && !trackPoint.hasSensorDistance()) {
-            Log.d(TAG, "Ignoring TrackPoint as it has no distance.");
-            return false;
+            Duration minStorageInterval = Duration.ofSeconds(10); // TODO Should be configurable.
+            boolean shouldStore = lastStoredTrackPoint.getTime().plus(minStorageInterval)
+                    .isBefore(trackPoint.getTime());
+            if (!shouldStore) {
+                Log.d(TAG, "Ignoring TrackPoint as it has no distance (and sensor data is not new enough).");
+                return false;
+            } else {
+                insertTrackPoint(trackPoint, true);
+                return true;
+            }
         }
 
         Distance distanceToLastStoredTrackPoint;