Update app.py

app.py

@@ -256,7 +256,7 @@ returns the names, SMILES strings, molecular weights and logP values for the sim
       tool_choice = (None, None)
     else:
       tool_choice = (tool_choices[0].strip().lower(), None)
-  elif len(tool_choices) == 2:
+  elif len(tool_choices) > 1:
     if tool_choices[0].strip().lower() == 'none':
       tool_choice = (None, tool_choices[1].strip().lower())
     elif tool_choices[1].strip().lower() == 'none':