add basic error handling

app.py

@@ -35,6 +35,22 @@ from src.submission.submit import add_new_eval
 from src.submission.evaluate import calculate_metrics
 
 def handle_new_eval_submission(model_name, model_zip, model_link=None):
+    
+    if not model_name:
+        return "Please enter a model name."
+    
+    # check if the model name is already in the leaderboard
+    if model_name in leaderboard_df[AutoEvalColumn.model.name].values:
+        return "Model name already exists in the leaderboard. Please choose a different name."
+    
+    # check if the zip file is actually a zip file
+    if model_zip is None or not zipfile.is_zipfile(model_zip):
+        return "Please upload a valid zip file."
+    
+    # check if the model name is only one word
+    if len(model_name.split()) > 1:
+        return "Model name should be a single word with hyphens."
+    
     extraction_path = EVAL_RESULTS_PATH_BACKEND
 
     if not os.path.exists(extraction_path):