fix(perception-module): properly using getter of lazy-loading length

Signed-off-by: Moritz Schweppenhäuser <[email protected]>

fed/mosaic-application/src/main/java/org/eclipse/mosaic/fed/application/ambassador/simulation/perception/index/providers/WallTree.java

@@ -52,7 +52,7 @@ public void initialize() {
                         wall.getFromCorner().getCartesianPosition().toVector3d(),
                         wall.getToCorner().getCartesianPosition().toVector3d()
                 ));
-                if (wall.length > maxWallLength) {
+                if (wall.getLength() > maxWallLength) {
                     maxWallLength = wall.getLength();
                 }
             }