Added wrong persona error

app.py

@@ -34,7 +34,11 @@ def respond(
 ):
     messages = []
 
-    system_prompt = config[model]["personas"][persona] 
+    try:
+        system_prompt = config[model]["personas"][persona]
+    except KeyError:
+        supported_personas = list(config[model]["personas"].keys())
+        raise gr.Error(f"Model '{model}' does not support persona '{persona}', only {supported_personas}")
     if system_prompt is not None:
         messages.append({"role": "system", "content": system_prompt})