#159 Add null-check to landingPadSizeFromPayload method

The 'landingPadSizeFromPayload()' method in 'ReceiveJournalDockedService.java' has been updated to handle possibly null landing pads with the help of Optional. An Optional.ofNullable has been added to elegantly handle any potential null values of the payload's landing pads. This offers a more robust and foolproof way of mapping landing pad sizes.

exploration-module/src/main/java/io/edpn/backend/exploration/application/service/ReceiveJournalDockedService.java

@@ -19,6 +19,7 @@
 
 import java.time.LocalDateTime;
 import java.util.Map;
+import java.util.Optional;
 import java.util.concurrent.ExecutorService;
 import java.util.stream.Collectors;
 
@@ -65,11 +66,12 @@ private void createOrUpdateFromPayload(DockedMessage.V1.Payload payload, LocalDa
     }
 
     private Map<LandingPadSize, Integer> landingPadSizeFromPayload(DockedMessage.V1.Payload payload) {
-        return Map.of(
-                LandingPadSize.LARGE, payload.landingPads().large(),
-                LandingPadSize.MEDIUM, payload.landingPads().medium(),
-                LandingPadSize.SMALL, payload.landingPads().small()
-        );
+        return Optional.ofNullable(payload.landingPads())
+                .map(landingPads -> Map.of(
+                        LandingPadSize.LARGE, landingPads.large(),
+                        LandingPadSize.MEDIUM, landingPads.medium(),
+                        LandingPadSize.SMALL, landingPads.small()
+                )).orElse(null);
     }
 
     private Map<String, Double> stationEconomiesFromPayload(DockedMessage.V1.Payload payload) {