fix: [titlebar] AT issue

[Lighto-Ku]

set accessible name of treeview btn in titlebar

Log: fix test issue

[deepin-ci-robot]

deepin pr auto review

关键摘要:

• 在OptionButtonBox::initializeUi函数中，新增代码块没有处理d->treeViewButton为nullptr的情况，可能会导致空指针解引用。
• 新增代码块没有使用if语句，而是直接判断d->treeViewButton是否为nullptr，这可能会导致代码的可读性降低。

是否建议立即修改:

• 是

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Johnson-zs, Lighto-Ku

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• debian/deepin/OWNERS

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[Lighto-Ku]

/merge