Woof plugin crashes when Woof action is run

In Do 0.6.0.1 (current trunk), attempting to send a file with Woof! results in an uncaught exception:

Unhandled Exception: System.ArgumentNullException: Argument cannot be null.
Parameter name: stream
  at System.IO.StreamReader.Initialize (System.IO.Stream stream, System.Text.Encoding encoding, Boolean detect_encoding_from_bytemarks, Int32 buffer_size) [0x00000]
  at System.IO.StreamReader..ctor (System.IO.Stream stream, System.Text.Encoding encoding, Boolean detect_encoding_from_bytemarks, Int32 buffer_size) [0x00000]
  at System.IO.StreamReader..ctor (System.IO.Stream stream) [0x00000]
  at (wrapper remoting-invoke-with-check) System.IO.StreamReader:.ctor (System.IO.Stream)
  at Woof.WoofServer.ServeFile (System.String path) [0x00000]
  at Woof.WoofSendFileAction+<>c__CompilerGenerated6.<Perform>c__7 () [0x00000]