Fix: After deleting all conversation lists, the chat input box can still be used for input. #4907 (#4909)

### What problem does this PR solve?

Fix: After deleting all conversation lists, the chat input box can still
be used for input. #4907

### Type of change

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

web/src/components/llm-setting-items/index.tsx

@@ -54,7 +54,11 @@ const LlmSettingItems = ({ prefix, formItemLayout = {} }: IProps) => {
         {...formItemLayout}
         rules={[{ required: true, message: t('modelMessage') }]}
       >
-        <Select options={modelOptions} showSearch />
+        <Select
+          options={modelOptions}
+          showSearch
+          popupMatchSelectWidth={false}
+        />
       </Form.Item>
       <div className="border rounded-md">
         <div className="flex justify-between bg-slate-100 p-2 mb-2">