Update pages/chapter_index.py

pages/chapter_index.py

@@ -29,7 +29,7 @@ def dataframe_with_selections(df_chapters: pd.DataFrame, init_value: bool = Fals
     selected_rows = edited_df[edited_df.Select]
     return selected_rows.drop('Select', axis=1)
 
-if "selected_chapters" is not in st.session_state:
+if "selected_chapters" not in st.session_state:
     st.session_state['selected_chapters'] = []
 
 selected_chapters_list = st.session_state.selected_chapters