Refactor: Add fallback lazy bbox calculation

CityDoctorParent/CityDoctorModel/src/main/java/de/hft/stuttgart/citydoctor2/datastructure/CityObject.java

@@ -92,7 +92,10 @@ public abstract class CityObject extends GmlElement {
         this.bbox = bbox;
     }
 
-    public BoundingBox getBbox(){
+    public synchronized BoundingBox getBbox(){
+        if (bbox == null){
+            this.setBbox(BoundingBox.of(this));
+        }
         return bbox;
     }