refactor: 修改SvgIcon组件，未找到class显示未发现图标防止报错

frontend/src/components/SvgIcon/index.vue

@@ -14,7 +14,8 @@ export default {
   props: {
     iconClass: {
       type: String,
-      required: true
+      required: false,
+      default: 'non-existent'
     },
     className: {
       type: String,

frontend/src/icons/svg/non-existent.svg

+<?xml version="1.0" standalone="no"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><svg t="1653050060477" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="3697" xmlns:xlink="http://www.w3.org/1999/xlink" width="200" height="200"><defs><style type="text/css">@font-face { font-family: feedback-iconfont; src: url("//at.alicdn.com/t/font_1031158_u69w8yhxdu.woff2?t=1630033759944") format("woff2"), url("//at.alicdn.com/t/font_1031158_u69w8yhxdu.woff?t=1630033759944") format("woff"), url("//at.alicdn.com/t/font_1031158_u69w8yhxdu.ttf?t=1630033759944") format("truetype"); }
+</style></defs><path d="M512 953.6a441.6 441.6 0 1 1 0-883.2 441.6 441.6 0 0 1 0 883.2z m0-64a377.6 377.6 0 1 0 0-755.2 377.6 377.6 0 0 0 0 755.2z" p-id="3698"></path><path d="M182.1696 227.4304l45.2608-45.2608 614.4 614.4-45.2608 45.2608z" p-id="3699"></path></svg>
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