Response.send with error: 'String contains invalid characters.'

[Jonathan Dai]

I just loaded all my files info in Google Drive and send them out.
And I got the error 'String contains invalid characters.';

Uncaught Error: Illegal argument(s): String contains invalid characters.
Stack Trace:
#0      _UnicodeSubsetEncoder.convert (dart:convert/ascii.dart:83)
#1      Codec.encode (dart:convert/codec.dart:22)
#2      _IOSinkImpl.write (dart:io/io_sink.dart:288)
#3      _HttpOutboundMessage.write (dart:io/http_impl.dart:484)
#4      Response.send (package:start/src/response.dart:65:20)