fix: 构建报错

Former-commit-id: c0a09d5c93cea56774f3a6e54aee3cd23b5c352c

src/views/demo/signature.vue

@@ -1,5 +1,6 @@
 <script setup lang="ts">
 import { uploadFileApi } from "@/api/file";
+import { makeInstaller } from "element-plus";
 
 const imgUrl = ref("");
 const canvas = ref();
@@ -102,14 +103,17 @@ const handleSaveImg = () => {
 const dataURLtoFile = (dataurl: string, filename: string) => {
   const arr: string[] = dataurl.split(",");
   if (!arr.length) return;
-  const mime = arr[0]?.match(/:(.*?);/)[1];
-  const bstr = atob(arr[1]);
-  let n = bstr.length;
-  const u8arr = new Uint8Array(n);
-  while (n--) {
-    u8arr[n] = bstr.charCodeAt(n);
+
+  const mime = arr[0].match(/:(.*?);/);
+  if (mime && !mime.length) {
+    const bstr = atob(arr[1]);
+    let n = bstr.length;
+    const u8arr = new Uint8Array(n);
+    while (n--) {
+      u8arr[n] = bstr.charCodeAt(n);
+    }
+    return new File([u8arr], filename, { type: mime[0] });
   }
-  return new File([u8arr], filename, { type: mime });
 };
 // canvas 画图
 function paint(