sync: from linuxdeepin/qt5integration

[deepin-ci-robot]

Synchronize source files from linuxdeepin/qt5integration.

Source-pull-request: linuxdeepin/qt5integration#251

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deepin pr auto review

关键摘要:

• createUnresolveFont 函数中使用了 static 变量 sysFont 和 fixedFont，但没有在函数外部初始化这些变量，可能会导致未定义行为。
• createUnresolveFont 函数中的 setResolveMask 调用可能需要检查 font 是否为 nullptr，以避免潜在的空指针解引用。
• 在 font 函数中，sysFont 和 fixedFont 的初始化逻辑重复，可以考虑提取公共代码。
• font 函数中的 break 语句被替换为返回默认字体，这可能会改变原有的逻辑，需要确认这是否是预期的行为。

是否建议立即修改:
是