diff --git a/PathPlanning/RRT/rrt.py b/PathPlanning/RRT/rrt.py
index b590d7b1..4acea0c1 100644
--- a/PathPlanning/RRT/rrt.py
+++ b/PathPlanning/RRT/rrt.py
@@ -140,7 +140,7 @@ class RRT:
         plt.clf()
         # for stopping simulation with the esc key.
         plt.gcf().canvas.mpl_connect('key_release_event',
-                lambda event: [exit(0) if event.key == 'escape' else None])
+                                     lambda event: [exit(0) if event.key == 'escape' else None])
         if rnd is not None:
             plt.plot(rnd.x, rnd.y, "^k")
         for node in self.node_list:
@@ -175,6 +175,10 @@ class RRT:
 
     @staticmethod
     def check_collision(node, obstacleList):
+
+        if node is None:
+            return False
+
         for (ox, oy, size) in obstacleList:
             dx_list = [ox - x for x in node.path_x]
             dy_list = [oy - y for y in node.path_y]