cocos creator 3.3 bug: Richtext imageOffset没有赋值

Creator 3.x
#1

cocos creator 3.3 Richtext imageOffset没有赋值

#2

@gameMaster @215194780 @jare @itharbors

#3

3.4 已修复，相关pr:https://github.com/cocos-creator/engine/pull/9778