Revert "fix for invalid tail starts being appended, if tail starts before the race"

This reverts commit bbdc6cedd6.

java/com.sap.sailing.domain/src/com/sap/sailing/domain/tracking/impl/GPSFixTrackImpl.java

@@ -414,7 +414,13 @@ public class GPSFixTrackImpl<ItemType, FixType extends GPSFix> extends MappedTra
         final Position result;
         // TODO bug #346: compute a confidence value for the position returned based on time difference between fix(es) and timePoint; consider using Taylor approximation of more fixes around timePoint to predict and weigh position
         if (lastFixAtOrBefore == null) {
-            result = null;
+            if (firstFixAtOrAfter == null) {
+                // no fix at all; cannot determine a position
+                result = null;
+            } else {
+                // only one fix valid; extrapolate or use unchanged
+                result = getEstimatedPosition(timePoint, firstFixAtOrAfter, extrapolate);
+            }
         } else {
             if (firstFixAtOrAfter == null) {
                 // only one fix valid; extrapolate or use unchanged