fix: handle empty meetings in changlog [skip ci]

Author: Josh-Cena

ferry/database/generate_changelog.py

@@ -195,11 +195,11 @@ def print_course_changes(
             old_meetings = cast(pd.DataFrame, old).apply(
                 lambda row: f"{print_days_of_week(row['days_of_week'])} {row['start_time']}–{row['end_time']} {location_info.loc[row['location_id']]['name'] if not pd.isna(row['location_id']) else ''}",
                 axis=1,
-            )
+            ) if not old.empty else []
             new_meetings = cast(pd.DataFrame, new).apply(
                 lambda row: f"{print_days_of_week(row['days_of_week'])} {row['start_time']}–{row['end_time']} {location_info.loc[row['location_id']]['name'] if not pd.isna(row['location_id']) else ''}",
                 axis=1,
-            )
+            ) if not new.empty else []
             res += f"  - Meetings: {", ".join(old_meetings) or "N/A"} → {", ".join(new_meetings) or "N/A"}\n"
         elif column == "listings":
             old_listings = cast(pd.DataFrame, old).apply(create_listing_link, axis=1)