Fix a missing_return analyzer error in a code example (#33468)
Fix a missing_return analyzer error in a code example (#33468)

This will fix a failure in dev/bots/analyze-sample-code.dart when using
the tip of tree Dart SDK.
cbracken/flutter,flutter/flutter,tvolkert/flutter,cbracken/flutter,flutter/flutter,tvolkert/flutter,Hixie/flutter,flutter/flutter,tvolkert/flutter,flutter/flutter,cbracken/flutter,cbracken/flutter,tvolkert/flutter,flutter/flutter,flutter/flutter,Hixie/flutter,Hixie/flutter,Hixie/flutter,tvolkert/flutter,tvolkert/flutter,cbracken/flutter,cbracken/flutter,Hixie/flutter,cbracken/flutter,tvolkert/flutter,cbracken/flutter,Hixie/flutter,flutter/flutter,Hixie/flutter,Hixie/flutter,flutter/flutter,flutter/flutter,flutter/flutter,cbracken/flutter,cbracken/flutter,tvolkert/flutter,tvolkert/flutter,Hixie/flutter,Hixie/flutter,tvolkert/flutter