Added error handling for deleting services

src/main/java/com/cpsc329pm/DeleteServiceSceneController.java

@@ -54,21 +54,40 @@ public class DeleteServiceSceneController {
         if (username.equals(confirmUser)) {
             try {
                 DataStorage ds = new DataStorage("master_login.json");
+
+                // Check if the service exists
+                Data existingData = ds.getData(platform, username);
+                if (existingData == null) {
+                    // If the service doesn't exist, show error alert
+                    Alert alert = new Alert(Alert.AlertType.ERROR);
+                    alert.setTitle("Delete Service");
+                    alert.setHeaderText("Error");
+                    alert.setContentText("No service found with the provided platform and username.");
+                    alert.showAndWait();
+                    return; // Exit method early if service doesn't exist
+                }
+
+                // If service exists, proceed with deletion
                 ds.deleteData(platform, username);
                 ds.saveToJSON();
+
                 Alert alert = new Alert(Alert.AlertType.INFORMATION);
                 alert.setTitle("Delete Service");
                 alert.setHeaderText("Success");
                 alert.setContentText("Service deleted successfully.");
                 alert.showAndWait();
+
+                // Reload the main page
                 Parent root = FXMLLoader.load(getClass().getResource("MainPage.fxml"));
                 Stage stage = (Stage) ((Node) event.getSource()).getScene().getWindow();
                 stage.setScene(new Scene(root));
                 stage.show();
+
             } catch (Exception e) {
                 e.printStackTrace();
             }
         } else {
+            // If username does not match the confirm username field
             Alert alert = new Alert(Alert.AlertType.ERROR);
             alert.setTitle("Delete Service");
             alert.setHeaderText("Error");