more robust error checking

1 files changed, 1 insertions, 1 deletions

diff --git a/tautils.py b/tautils.py
index c7587c4..e7888ea 100644
--- a/tautils.py
+++ b/tautils.py
@@ -429,7 +429,7 @@ def uncollapse_forks(top, looping=False):
 def collapse_stack(top):
     """ Hide all the blocks between the sandwich top and sandwich bottom. """
     # First uncollapse any nested stacks
-    if top.spr == None:
+    if top == None or top.spr == None:
         return
     uncollapse_forks(top)
     _hit_bottom = False