fix: icon size changed on paletteChanged

[kegechen]

只在初始化和 sourceSizeChanged 时更新图标大小 防止出现 dpr > 1.0 时未设置 sourceSize 的 item 在 updatePlayer 时图标一直放大 没有设置 sourceSize 会根据图片大小去 match dci 中的图标大小

[kegechen]

see https://github.com/linuxdeepin/dtkdeclarative/pull/376

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This pull-request has been approved by: FeiWang1119, kegechen

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关键摘要:

• 在updatePlayerIconSize()函数调用后没有检查返回值，可能会导致未处理的初始化错误。
• updatePlayerIconSize()函数调用可能依赖于sourceSizeChanged信号，但当前的调用顺序没有反映这种依赖关系。
• 注释中的“只在初始化和 sourceSizeChanged 时更新图标大小”描述可能与实际的代码逻辑不一致，需要确认是否所有相关信号都已经正确连接。

是否建议立即修改:

• 是