support pagination in webui preview

Former-commit-id: f2307e26b9c2ce5d60917cce5a9638466ea676c8

src/llmtuner/webui/chatter.py

@@ -1,3 +1,4 @@
+import gradio as gr
 from gradio.components import Component # cannot use TYPE_CHECKING here
 from typing import TYPE_CHECKING, Any, Dict, Generator, List, Optional, Tuple
 
@@ -28,16 +29,17 @@ class WebChatModel(ChatModel):
     def load_model(self, data: Dict[Component, Any]) -> Generator[str, None, None]:
         get = lambda name: data[self.manager.get_elem_by_name(name)]
         lang = get("top.lang")
+        error = ""
         if self.loaded:
-            yield ALERTS["err_exists"][lang]
-            return
+            error = ALERTS["err_exists"][lang]
+        elif not get("top.model_name"):
+            error = ALERTS["err_no_model"][lang]
+        elif not get("top.model_path"):
+            error = ALERTS["err_no_path"][lang]
 
-        if not get("top.model_name"):
-            yield ALERTS["err_no_model"][lang]
-            return
-
-        if not get("top.model_path"):
-            yield ALERTS["err_no_path"][lang]
+        if error:
+            gr.Warning(error)
+            yield error
             return
 
         if get("top.checkpoints"):