T91111: possible out of range when iterating over Math Vis item list

While preparing T91111 i found an issue with out of date index after my recent changes.
The problem is:

bpy.context.window_manager.MathVisProp can be "0" even when the list is actually empty.

This patch fixes the index issue, although the true cause might still be found elsewhere.
there is more to fix, so this is only a first step to a complete fix.

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D12390

1 files changed, 6 insertions, 2 deletions

diff --git a/space_view3d_math_vis/draw.py b/space_view3d_math_vis/draw.py
index 0420044e..33f6a965 100644
--- a/space_view3d_math_vis/draw.py
+++ b/space_view3d_math_vis/draw.py
@@ -149,8 +149,12 @@ def draw_callback_view():
         bgl.glDepthFunc(bgl.GL_LESS)
 
     data_matrix, data_quat, data_euler, data_vector, data_vector_array = utils.console_math_data()
-    active_index = settings.index
-    active_key = prop_states[active_index].name if active_index >= 0 else None
+    if settings.index in range(0,len(prop_states)):
+        active_index = settings.index
+        active_key = prop_states[active_index].name
+    else:
+        active_index = -1
+        active_key = None
 
     if data_vector:
         coords = [tuple(vec.to_3d()) for vec in data_vector.values()]