Apparently latitude/longitude/altitude of a GW are optional fields, so prepare for that and don't report these GWs.

workspace/ttnhabbridge/src/main/java/nl/sikken/bertrik/TtnHabBridge.java

@@ -100,9 +100,14 @@ public final class TtnHabBridge {
             // create listeners
             final List<HabReceiver> receivers = new ArrayList<>();
             for (TtnMessageGateway gw : message.getMetaData().getMqttGateways()) {
-                final HabReceiver receiver = new HabReceiver(gw.getId(),
-                        new Location(gw.getLatitude(), gw.getLongitude(), gw.getAltitude()));
-                receivers.add(receiver);
+            	final Double latitude = gw.getLatitude();
+            	final Double longitude = gw.getLongitude();
+            	final Double altitude = gw.getAltitude();
+            	if ((latitude != null) && (longitude != null) && (altitude != null)) {
+	                final HabReceiver receiver = new HabReceiver(gw.getId(),
+	                        new Location(gw.getLatitude(), gw.getLongitude(), gw.getAltitude()));
+	                receivers.add(receiver);
+            	}
             }
 
             // send listener data

workspace/ttnhabbridge/src/main/java/nl/sikken/bertrik/hab/ttn/TtnMessageGateway.java

@@ -19,13 +19,13 @@ public final class TtnMessageGateway {
     private String time;
     
     @JsonProperty("latitude")
-    private double latitude;
+    private Double latitude;
     
     @JsonProperty("longitude")
-    private double longitude;
+    private Double longitude;
     
     @JsonProperty("altitude")
-    private double altitude;
+    private Double altitude;
 
     public String getId() {
         return id;
@@ -39,15 +39,15 @@ public final class TtnMessageGateway {
         return time;
     }
 
-    public double getLatitude() {
+    public Double getLatitude() {
         return latitude;
     }
 
-    public double getLongitude() {
+    public Double getLongitude() {
         return longitude;
     }
 
-    public double getAltitude() {
+    public Double getAltitude() {
         return altitude;
     }