Fix：修复搜索不能替换为空字符串的问题

simple-mind-map/full.js

@@ -2,6 +2,7 @@ import MindMap from './index'
 import MiniMap from './src/plugins/MiniMap.js'
 import Watermark from './src/plugins/Watermark.js'
 import KeyboardNavigation from './src/plugins/KeyboardNavigation.js'
+import ExortXMind from './src/plugins/ExortXMind.js'
 import ExportPDF from './src/plugins/ExportPDF.js'
 import Export from './src/plugins/Export.js'
 import Drag from './src/plugins/Drag.js'
@@ -11,6 +12,7 @@ import RichText from './src/plugins/RichText'
 import NodeImgAdjust from './src/plugins/NodeImgAdjust.js'
 import TouchEvent from './src/plugins/TouchEvent.js'
 import Search from './src/plugins/Search.js'
+import Painter from './src/plugins/Painter.js'
 import xmind from './src/parse/xmind.js'
 import markdown from './src/parse/markdown.js'
 import icons from './src/svg/icons.js'
@@ -30,6 +32,7 @@ MindMap
   .usePlugin(Watermark)
   .usePlugin(Drag)
   .usePlugin(KeyboardNavigation)
+  .usePlugin(ExortXMind)
   .usePlugin(ExportPDF)
   .usePlugin(Export)
   .usePlugin(Select)
@@ -38,5 +41,6 @@ MindMap
   .usePlugin(TouchEvent)
   .usePlugin(NodeImgAdjust)
   .usePlugin(Search)
+  .usePlugin(Painter)
 
 export default MindMap

simple-mind-map/src/plugins/Search.js

@@ -90,7 +90,8 @@ class Search {
   // 替换当前节点
   replace(replaceText) {
     if (
-      isUndef(replaceText) ||
+      replaceText === null ||
+      replaceText === undefined ||
       !this.isSearching ||
       this.matchNodeList.length <= 0
     )
@@ -115,7 +116,8 @@ class Search {
   // 替换所有
   replaceAll(replaceText) {
     if (
-      isUndef(replaceText) ||
+      replaceText === null ||
+      replaceText === undefined ||
       !this.isSearching ||
       this.matchNodeList.length <= 0
     )