Cascader: 多选和过滤情况下，修复关键字没有清空的bug

[shangyaw]

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[webvs2]

Can you give an example of a recurrence of a problem

[shangyaw]

Can you give an example of a recurrence of a problem

After I type and select a keyword for the second time, the keyword won't be emptied

[shangyaw]

Can you give an example of a recurrence of a problem

the pic is on the above, hope you review the code ASAP, thanks