diff --git a/core/shape.py b/core/shape.py
index 9eef4ef..be38a9a 100644
--- a/core/shape.py
+++ b/core/shape.py
@@ -148,8 +148,8 @@ def get_picker_data(collection):
     
     canvas_coords = [canvas.matrix_world@Vector((p.co)) for p in canvas_points]
 
-    height = abs(max(canvas_coords).y - min(canvas_coords).y)
-    width = abs(max(canvas_coords).x - min(canvas_coords).x)
+    height = abs(max(co.y for co in canvas_coords) - min(co.y for co in canvas_coords))
+    width = abs(max(co.x for co in canvas_coords) - min(co.x for co in canvas_coords))
 
     center = sum(canvas_coords, Vector()) / len(canvas_coords)
     scale = 2048 / max(height, width)# Reference height for the canvas
diff --git a/operators/shape.py b/operators/shape.py
index 6825a77..d4e478c 100644
--- a/operators/shape.py
+++ b/operators/shape.py
@@ -95,7 +95,7 @@ class RP_OT_mirror_shape(Operator):
                 continue
 
             for mod in ob.modifiers:
-                if (mod.type == 'NODES' and mod.node_group.name == 'Symmetrize' and
+                if (mod.type == 'NODES' and mod.node_group and mod.node_group.name == 'Symmetrize' and
                         mod.get('Socket_2') in objects):
                 
                     bpy.data.objects.remove(ob)
@@ -124,7 +124,7 @@ class RP_OT_mirror_shape(Operator):
             for mod in list(flipped_object.modifiers):
                 flipped_object.modifiers.remove(mod)
 
-            # Add symmetrize modifier
+            # Add symmetrize modifier TODO add it into a resource
             mod = flipped_object.modifiers.new(name='Symmetrize', type='NODES')
             mod.node_group = bpy.data.node_groups['Symmetrize']
             mod['Socket_2'] = ob