Uncaught exception in server

[AsturaPhoenix]

This exception is eventually caught, but we probably don't register an error handler early enough for Dart to consider the error caught. This is probably a future in a cache. The traces weren't particularly useful; one instance was an http.ClientException from interleave2x32.

In the error logs:

[2023-07-30 01:40:03.554665Z] WARNING AquamarineServer: Failed to fetch f025.20230729.t21z
        Connection closed while receiving data
#0      IOClient.send.<anonymous closure> (package:http/src/io_client.dart:82:13)
#1      Stream.handleError.<anonymous closure> (dart:async/stream.dart:923:16)

This probably only impacts running in debug mode, where the VM stops on uncaught asynchronous exceptions.

[AsturaPhoenix]

This is probably spurious. Tests of this test case do not complain of an uncaught exception unless observatory is attached, so this is likely related to dart-lang/sdk#47985 and friends. That is to say, the uncaught exception handler for the test zone is never invoked; only the debugger complains. I suspect the latter is using less robust/correct logic to determine whether an exception is caught.

Will close this issue after committing a test.