A hang occurs when typing `source /dev/stdin`

Describe the bug
Nushel hangs when trying to type source /dev/stdin.

To Reproduce

1. Open Nushell
2. Try to type source /dev/stdin
3. It hangs when pressing the last N key and the letter n is not displayed

Expected behavior
It should not hang.

Screenshots

Configuration (please complete the following information):

Run version | pivot and paste the output to show OS, features, etc.

> version | pivot
  #        Column0                                               Column1
────────────────────────────────────────────────────────────────────────────────────────────────────────────────
  0   version              0.33.0
  1   build_os             linux-x86_64
  2   rust_version         rustc 1.53.0
  3   cargo_version        cargo 1.53.0
  4   pkg_version          0.33.0
  5   build_time           2021-07-20 18:48:12
  6   build_rust_channel   release
  7   features             clipboard-cli, ctrlc, default, ptree, rustyline, term, trash, uuid, which, zip
  8   installed_plugins    binaryview, chart bar, chart line, fetch, from bson, from sqlite, inc, match, post,
                           ps, query json, s3, selector, start, sys, textview, to bson, to sqlite, tree, xpath

Add any other context about the problem here.

Start by reproducing source /dev/stdin in Nushell on Linux and inspect the interactive input path where the final n is entered. Trace why input stops responding, then verify that the command no longer hangs and the complete text is displayed.