first location fix

BLL.App/Services/GpsLocationService.cs

@@ -37,21 +37,24 @@ namespace BLL.App.Services
 
             var gpsSession = await UOW.GpsSessions.FirstOrDefaultAsync(gpsLocation.GpsSessionId, gpsLocation.AppUserId);
             var lastLocation = await UOW.GpsLocations.LastInSessionAsync(gpsSession.Id);
-            // calculate the metrics
-            var distance = getDistance(gpsLocation, lastLocation);
-            var vertical = getVerticalDistance(gpsLocation, lastLocation);
-            gpsSession.Distance += distance;
-            if (vertical < 0)
+            if (lastLocation != null)
             {
-                gpsSession.Descent += Math.Abs(vertical);
-            } else if (vertical > 0)
-            {
-                gpsSession.Descent += vertical;
-            }
+                // calculate the metrics
+                var distance = getDistance(gpsLocation, lastLocation);
+                var vertical = getVerticalDistance(gpsLocation, lastLocation);
+                gpsSession.Distance += distance;
+                if (vertical < 0)
+                {
+                    gpsSession.Descent += Math.Abs(vertical);
+                } else if (vertical > 0)
+                {
+                    gpsSession.Descent += vertical;
+                }
 
-            gpsSession.Duration = (gpsSession.RecordedAt - lastLocation.RecordedAt).TotalSeconds; 
+                gpsSession.Duration = (gpsSession.RecordedAt - lastLocation.RecordedAt).TotalSeconds; 
                 
-            await UOW.GpsSessions.UpdateAsync(gpsSession);
+                await UOW.GpsSessions.UpdateAsync(gpsSession);
+            }
             
             return base.Add(gpsLocation);
         }