修复预处理代码中的var let

Author: garywill

data/pre_common/functions.js

@@ -207,7 +207,7 @@ function combineCharObj(c , fromMap1, fromMap2)
 
 function unionSet(setA, setB) {
     let _union = new Set(setA);
-    for ( var let elem of setB) {
+    for ( var  elem of setB) {
         _union.add(elem);
     }
     return _union;