Remove unnecessary original_on variable

https://claude.ai/code/session_01F7cbsuGUbfDoW1oDdiGqf5

Author: claude

src/nested_pandas/series/packer.py

@@ -93,7 +93,6 @@ def pack_flat(
     nested_pandas.series.dtype.NestedDtype : The dtype of the output series.
     nested_pandas.series.packer.pack_lists : Pack a dataframe of nested arrays.
     """
-    original_on = on
     if on is not None:
         df = df.set_index(on)
     # pandas knows when index is pre-sorted, so it would do nothing if it is already sorted
@@ -103,8 +102,8 @@ def pack_flat(
     except ValueError:
         # Check if the error is due to NaN values and raise a more informative message
         if any(sorted_flat.index.get_level_values(i).hasnans for i in range(sorted_flat.index.nlevels)):
-            if original_on is not None:
-                cols = [original_on] if isinstance(original_on, str) else list(original_on)
+            if on is not None:
+                cols = [on] if isinstance(on, str) else list(on)
                 raise ValueError(
                     f"Column(s) {cols} contain NaN values. "
                     "NaN values are not supported because they cannot be used for grouping rows. "