return empty string when attribute value is not string type

Author: laispace

lib/js2xml.js

@@ -12,6 +12,10 @@ function escapeSingleQuotes (value) {
 
 function stringifyAttribute (attrs, key, keepDoubleQuotes) {
   const value = attrs[key]
+  if (typeof value !== 'string') {
+    console.error('invalid attribute type:', attrs, key)
+    return `${key}=''`
+  }
   try {
     if (keepDoubleQuotes) {
       return `${key}='${escapeSingleQuotes(value)}'`