Update app.py

app.py

@@ -171,13 +171,14 @@ def merge_with_master(processed_files):
         return None
 
     master_df = master_file["df"]
+    if master_df.empty: # Check if master_df is empty. If so, no point merging.
+        st.warning(f"Master DataFrame '{master_file['filename']}' is empty. Merging will result in an empty DataFrame.")
+        return pd.DataFrame() # Return empty DataFrame
+
     master_keys = master_file["analysis"].get("key_columns", [])
     st.write(f"Using '{master_file['filename']}' as master with key columns: {master_keys}")
     merged_df = master_df
 
-    if merged_df.empty: # Check if master_df is empty. If so, no point merging.
-        st.warning(f"Master DataFrame '{master_file['filename']}' is empty. Merging will result in an empty DataFrame.")
-        return merged_df
 
     for other in other_files:
         other_df = other["df"]