我收到此错误，这一切都是在我从v0.4.4切换到Flutter版本v0.5.1之后发生的，有人知道我可以做什么来解决此问题吗？ 该项目几乎已经准备就绪，现在无法编译！
MacBook-Pro-de-Tiago:flutter_app2 tiagosito$ flutter doctor Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel beta, v0.5.1, on Mac OS X 10.13.5 17F77, locale pt-BR)
[✓] Android toolchain - develop for Android devices (Android SDK 27.0.3) [✓] iOS toolchain - develop for iOS devices (Xcode 9.4.1)
[✓] Android Studio (version 3.1)
[✓] Connected devices (2 available)
• No issues found!
MacBook-Pro-de-Tiago:flutter_app2 tiagosito$
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