Fix nullptr exception when using do-while

Using of 'instanceof' cannot determine whether 'nextParent' is non-null during the first loop in do-while, so when 'focused.getParent()' outside the loop returns null, the loop body will trigger a null pointer exception. Therefore, the conditional judgment needs to be covered in every loop.

Test:UAT
Bug: 336205346

Change-Id: I78374410d928009ea9b99630cae2fbea24ba8ab6
Signed-off-by: zhuning3 <zhuning3@xiaomi.corp-partner.google.com>