refactor: 按照 code review 建议做些小修改

Author: Jeff-Tian

src/packages/uploader/demos/h5/demo15.tsx

@@ -4,7 +4,7 @@ import { Uploader } from '@nutui/nutui-react'
 const Demo15 = () => {
   return (
     <>
-      <Uploader enablePasteUpload />
+      <Uploader enablePasteUpload uploadLabel="点击上传或粘贴图片" />
     </>
   )
 }

src/packages/uploader/doc.md

@@ -139,6 +139,8 @@ app.post('/upload', upload.single('file'), (req, res) => {
 
 ### 浏览器中粘贴图片上传
 
+在浏览器中可以通过 Ctrl+V（Mac 上是 Cmd+V） 或右键粘贴图片进行上传。
+
 :::demo
 
 <CodeBlock src='h5/demo15.tsx'></CodeBlock>

src/packages/uploader/uploader.tsx

@@ -396,7 +396,7 @@ const InternalUploader: ForwardRefRenderFunction<
 
       const files: File[] = []
 
-      if (clipboardData.items && clipboardData.items.length) {
+      if (clipboardData?.items && clipboardData.items.length) {
         for (let i = 0; i < clipboardData.items.length; i++) {
           const item = clipboardData.items[i]
           if (item.kind === 'file' && item.type.startsWith('image/')) {
@@ -406,7 +406,7 @@ const InternalUploader: ForwardRefRenderFunction<
             }
           }
         }
-      } else if (clipboardData.files && clipboardData.files.length) {
+      } else if (clipboardData?.files && clipboardData.files.length) {
         for (let i = 0; i < clipboardData.files.length; i++) {
           const file = clipboardData.files[i]
           if (file.type.startsWith('image/')) {