Collection Manager: Fix invalid list index. Task: T69577

Fix error when trying to add a new collection if the selected
collection was deleted using the Outliner.

object_collection_manager/__init__.py

@@ -22,7 +22,7 @@ bl_info = {
     "name": "Collection Manager",
     "description": "Manage collections and their objects",
     "author": "Ryan Inch",
-    "version": (2, 7, 23),
+    "version": (2, 7, 24),
     "blender": (2, 80, 0),
     "location": "View3D - Object Mode (Shortcut - M)",
     "warning": '',  # used for warning icon and text in addons panel

object_collection_manager/ui.py

@@ -335,6 +335,10 @@ class CollectionManager(Operator):
 
         self.view_layer = view_layer.name
 
+        # make sure list index is valid
+        if cm.cm_list_index >= len(cm.cm_list_collection):
+            cm.cm_list_index = -1
+
         # check if expanded & history/buffer state still correct
         if collection_state:
             new_state = generate_state()