sync: from linuxdeepin/dtkgui

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Synchronize source files from linuxdeepin/dtkgui.

Source-pull-request: linuxdeepin/dtkgui#279

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关键摘要:

• 在DWindowManagerHelper::instance()函数中，treelandWMHGlobal被直接返回，但没有检查其是否为空或未初始化。
• TreelandWindowManagerHelper类中的信号hasBlurWindowChanged()和hasNoTitlebarChanged()在PersonalizationManager::activeChanged信号连接时被发射，但没有检查PersonalizationManager实例是否为空或未初始化。
• TreelandWindowManagerHelper类中的hasBlurWindow()、hasComposite()和hasNoTitlebar()函数直接返回PersonalizationManager::instance()->isSupported()，但没有处理PersonalizationManager实例可能为空的情况。

是否建议立即修改:
是

• 应该在DWindowManagerHelper::instance()函数中添加对treelandWMHGlobal的空值检查。
• 在TreelandWindowManagerHelper类中，应该添加对PersonalizationManager::instance()的空值检查，并确保在PersonalizationManager实例为空时不会发射信号。
• 在TreelandWindowManagerHelper类中的hasBlurWindow()、hasComposite()和hasNoTitlebar()函数中，应该添加对PersonalizationManager::instance()的空值检查，并处理可能为空的情况。