add error handling for duplicate image votes and fix DataFrame concatenation

app.py

@@ -80,6 +80,11 @@ def update_vote(
     df = pd.read_csv(file_path)
     print(df)
 
+    # if the df has the image path of the image, raise an error
+    if image in df["image_path"].tolist():
+        st.error("You have already voted for this image")
+        st.stop()
+
     new_row = pd.DataFrame(
         {
             "image_path": [image],
@@ -92,7 +97,7 @@ def update_vote(
         }
     )
 
-    df = df.concat([df, new_row])
+    df = pd.concat([df, new_row], ignore_index=True)
     df.to_csv(file_path, index=False)
 
     # push the file to the dataset