Improve error handling

app.py

@@ -19,8 +19,8 @@ operations = {"+": add, "-": sub}
 def parse_expression(input):
     try:
         return expression.parseString(input)
-    except ParseException as pe:
-        raise gr.Error(f"Syntax error at {pe.loc}: {pe.msg}")
+    except ParseException as e:
+        raise gr.Error(f"Parsing error: {e.msg} at position [{e.loc}].")
 
 
 def evaluate_expression(input):
@@ -52,6 +52,9 @@ def expression_to_vectors(input):
 
 
 def get_results(expression):
+    if len(expression) < 1:
+        raise gr.Error("Please provide an expression.")
+
     vectors = expression_to_vectors(expression)
     similarity_scores = cosine_similarity([vectors], all_vectors)[0]
     top_indices = np.argsort(similarity_scores)[::-1]