!4 修复一级类目无二级类目时 后台报数组越界异常

Merge pull request !4 from youc3576/master

litemall-wx-api/src/main/java/org/linlinjava/litemall/wx/web/WxGoodsController.java

@@ -189,7 +189,7 @@ public class WxGoodsController {
         if (cur.getPid() == 0) {
             parent = cur;
             children = categoryService.queryByPid(cur.getId());
-            cur = children.get(0);
+            cur = children.size()>0?children.get(0):cur;
         } else {
             parent = categoryService.findById(cur.getPid());
             children = categoryService.queryByPid(cur.getPid());