type error correction

app.py

@@ -64,7 +64,7 @@ def download_button(object_to_download, download_filename, button_text, pickle_i
                 encoding='utf-8',
                 index=False,
                 header=True,
-                na_rep=''
+                na_rep='n/a',
             )
             towrite.seek(0)
 
@@ -114,7 +114,14 @@ def download_button(object_to_download, download_filename, button_text, pickle_i
 
     return dl_link
 
-
+st.markdown(
+    '''
+        # COnvert Revit IDs to GUIDs
+        Provide any spreadsheet (using a dropbox link) that has a column of revit IDs.
+        Select the sheet witin the spreadsheet and the column with the IDs.
+        Only the selected sheet will be returned, you can cut and paste the sheet back into the origial spreadsheet.
+    '''
+)
 
 
 cobie_file_button = st.text_input("Dropbox link to COBie file", key="cobie_file_button")
@@ -142,7 +149,9 @@ if tabs:
 
     df = cobie_file.parse(selected_sheet)
 
-    st.write(df)
+    if type(df) == pd.DataFrame:
+
+        st.write(df)
 
     # st.markdown(download_button(df, 'COBieIDs.xlsx', 'Download COBieIDs.xlsx'), unsafe_allow_html=True)