fixed gps page

lib/model/gps_data.dart

@@ -4,6 +4,7 @@ class GpsData {
   String event_code;
   double lat;
   double lon;
+  int is_checkin;
   int created_at;
 
   GpsData(
@@ -12,7 +13,8 @@ class GpsData {
       required this.event_code,
       required this.lat,
       required this.lon,
-      required this.created_at});
+      required this.created_at,
+      this.is_checkin = 0});
 
   factory GpsData.fromMap(Map<String, dynamic> json) {
     return GpsData(
@@ -21,6 +23,7 @@ class GpsData {
         event_code: json["event_code"],
         lat: json["lat"],
         lon: json["lon"],
+        is_checkin: json["is_checkin"],
         created_at: json["created_at"]);
   }
 
@@ -31,6 +34,7 @@ class GpsData {
       'event_code': event_code,
       'lat': lat,
       'lon': lon,
+      'is_checkin': is_checkin,
       'created_at': created_at
     };
   }