bug#20219: crash of the repl

[Andrew Engelbrecht]

i opened guile, then pressed ctrl-c, then a bunch of other buttons
including ctrl-d and enter. eventually it crashed:


$ guile
(GNU Guile 2.0.11
Copyright (C) 1995-2014 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)>^C^CWhile reading expressioBacktrace:
In ice-9/boot-9.scm:
 157: 12 [catch #t #<catch-closure 9fd3000> ...]
In unknown file:
   ?: 11 [apply-smob/1 #<catch-closure 9fd3000>]
In ice-9/boot-9.scm:
  63: 10 [call-with-prompt prompt0 ...]
In ice-9/top-repl.scm:
  33: 9 [#<procedure a11a420 at ice-9/top-repl.scm:31:6 (thunk)>
#<procedure a11a3a0 at ice-9/top-repl.scm:66:5 ()>]
  76: 8 [#<procedure a11a3a0 at ice-9/top-repl.scm:66:5 ()>]
In system/repl/repl.scm:
 142: 7 [start-repl* scheme #f #<procedure prompting-meta-read (repl)>]
 168: 6 [run-repl* # #<procedure prompting-meta-read (repl)>]
 123: 5 [#<procedure a11abe0 at system/repl/repl.scm:118:4 (key . args)>
signal ...]
In ice-9/format.scm:
1593: 4 [format #<output: file /dev/pts/1> "While reading expression:\n"]
 766: 3 [format:format-work "While reading expression:\n" ()]
  83: 2 [anychar-dispatch]
In unknown file:
   ?: 1 [char=? #\o #\newline]
   ?: 0 [scm-error signal #f "User interrupt" () (2)]

ERROR: In procedure scm-error:
ERROR: User interrupt