fix: check listener exist el

Author: hunterliu1003

dist/VueFinalModal.esm.js

@@ -50,10 +50,10 @@ const pointerType = {
   }
 }
 export const addListener = (type, el, callback) => {
-  el.addEventListener(pointerType[type].pc, callback)
-  el.addEventListener(pointerType[type].m, callback, { passive: false })
+  el && el.addEventListener(pointerType[type].pc, callback)
+  el && el.addEventListener(pointerType[type].m, callback, { passive: false })
 }
 export const removeListener = (type, el, callback) => {
-  el.removeEventListener(pointerType[type].pc, callback)
-  el.removeEventListener(pointerType[type].m, callback)
+  el && el.removeEventListener(pointerType[type].pc, callback)
+  el && el.removeEventListener(pointerType[type].m, callback)
 }