网络请求可能存在 Use-After-Free 问题，导致无法进行资源搜索

[LinQingYuu]

我的也是，开启debug模式后在搜索时会显示部分结果然后报错
类似[17:39:05.651] [DBG] [STA] 搜索过程中发生异常:System.ObjectDisposedException: The CancellationTokenSource has been disposed.
at System.Threading.CancellationTokenSource.get_Token()
at PCL.PageInstanceCompResource._Closure$__89-0._Lambda$__0()
[17:39:13.193] [INFO] [STA] [Report] FPS 64, 动画 11, 下载中 0（0 B/s）
[17:39:20.678] [DBG] [STA] 搜索过程中发生异常:System.ObjectDisposedException: The CancellationTokenSource has been disposed.
at System.Threading.CancellationTokenSource.get_Token()
at PCL.PageInstanceCompResource._Closure$__89-0._Lambda$__0()
[17:39:33.303] [INFO] [STA] [Report] FPS 38, 动画 1, 下载中 0（0 B/s）
[17:39:35.010] [DBG] [STA] 搜索过程中发生异常:System.ObjectDisposedException: The CancellationTokenSource has been disposed.
at PCL.PageInstanceCompResource._Closure$__89-0._Lambda$__0()

Originally posted by @gaoteng189 in #2738 (comment)