fix: Resolve the issue of not being able to repeatedly open ddf files

[starhcq]

Resolve the issue of not being able to repeatedly open ddf files

Log: Resolve the issue of not being able to repeatedly open ddf files
Bug: https://pms.uniontech.com/bug-view-270887.html

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关键摘要:

• 在CFileWatcher::doRun函数中，使用appQuit变量来控制文件读取循环的退出条件，这是一个改进的逻辑，避免了在文件读取过程中频繁检查是否退出。
• 添加了appQuit变量，但未在代码注释中说明其用途和作用。
• 使用了Lambda表达式来简化事件连接的代码，但未提供上下文以理解this指针的用途。
• 文件读取循环中的while条件现在检查了qApp->closingDown()，这可能是为了在应用程序正在退出时停止文件监视，但需要确认这是否是预期的行为。

是否建议立即修改:

• 是，建议添加必要的注释来解释appQuit变量的用途，以便其他开发者理解代码意图。
• 是，建议确认qApp->closingDown()的添加是否符合预期行为，并在代码中添加相应的注释说明。