handle project without top map

rest-api/src/main/java/lcsb/mapviewer/api/projects/models/ModelRestImpl.java

@@ -113,15 +113,17 @@ public class ModelRestImpl extends BaseRestImpl {
   private List<Map<String, Object>> createData(Project project) throws QueryException {
     List<Map<String, Object>> result = new ArrayList<>();
     Collection<ModelData> originalModels = getModelService().getModelsByProjectId(project.getProjectId());
-    ModelData topModel = project.getTopModel().getModelData();
     List<ModelData> models = new ArrayList<>();
-    for (ModelData model: originalModels) {
-      if (!Objects.equals(model.getId(), topModel.getId())) {
-        models.add(model);
+    if (project.getTopModel() != null) {
+      ModelData topModel = project.getTopModel().getModelData();
+      for (ModelData model : originalModels) {
+        if (!Objects.equals(model.getId(), topModel.getId())) {
+          models.add(model);
+        }
       }
+      result.add(getModel(topModel));
     }
     models.sort(ModelData.ID_COMPARATOR);
-    result.add(getModel(topModel));
     for (ModelData model2 : models) {
       result.add(getModel(model2));
     }