fix ol

Author: willmcgugan

src/textual/widgets/_option_list.py

@@ -320,6 +320,8 @@ def add_options(self, new_options: Iterable[OptionListContent]) -> Self:
             new_options: Content of new options.
         """
 
+        new_options = list(new_options)
+
         option_ids = [
             option._id
             for option in new_options
@@ -330,7 +332,6 @@ def add_options(self, new_options: Iterable[OptionListContent]) -> Self:
                 "New options contain duplicated IDs; Ensure that the IDs are unique."
             )
 
-        new_options = list(new_options)
         if not new_options:
             return self
         if new_options[0] is None: