fix: fixed the problem that the api will be called directly after selecting the chat assistant picture (#1034)

### What problem does this PR solve?

fix: fixed the problem that the api will be called directly after
selecting the chat assistant picture #1033

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

api/apps/dialog_app.py

     req = request.json
     dialog_id = req.get("dialog_id")
     name = req.get("name", "New Dialog")
+    icon = req.get("icon", "")
     description = req.get("description", "A helpful Dialog")
     top_n = req.get("top_n", 6)
     top_k = req.get("top_k", 1024)
                 "top_k": top_k,
                 "rerank_id": rerank_id,
                 "similarity_threshold": similarity_threshold,
-                "vector_similarity_weight": vector_similarity_weight
+                "vector_similarity_weight": vector_similarity_weight,
+                "icon": icon,
             }
             if not DialogService.save(**dia):
                 return get_data_error_result(retmsg="Fail to new a dialog!")

web/src/pages/chat/chat-configuration-modal/assistant-setting.tsx

 
   const uploadButtion = (
     <button style={{ border: 0, background: 'none' }} type="button">
-            <PlusOutlined />
-            <div style={{ marginTop: 8 }}>
-              {t('upload', { keyPrefix: 'common' })}
-            </div>
-          </button>
-  )
+      <PlusOutlined />
+      <div style={{ marginTop: 8 }}>{t('upload', { keyPrefix: 'common' })}</div>
+    </button>
+  );
 
   return (
     <section
         <Upload
           listType="picture-card"
           maxCount={1}
+          beforeUpload={() => false}
           showUploadList={{ showPreviewIcon: false, showRemoveIcon: false }}
         >
           {show ? uploadButtion : null}

web/src/pages/chat/chat-configuration-modal/index.tsx

 import PromptEngine from './prompt-engine';
 
 import { useTranslate } from '@/hooks/commonHooks';
+import { getBase64FromUploadFileList } from '@/utils/fileUtil';
 import styles from './index.less';
 
 const layout = {
     ]);
     const emptyResponse = nextValues.prompt_config?.empty_response ?? '';
 
-    const fileList = values.icon;
-    let icon;
-
-    if (Array.isArray(fileList) && fileList.length > 0) {
-      icon = fileList[0].thumbUrl;
-    }
+    const icon = await getBase64FromUploadFileList(values.icon);
 
     const finalValues = {
       dialog_id: initialDialog.id,