bug#38562: the installer crash when pressing shift+f2 or f12

[Brice Waegeneire]

Using the installer guix-system-install-1.0.1.x86_64-linux.iso it crash 
at least on the first page, the language selection one, when pressing 
shift+f2 or f12. The dumps are attached.In ice-9/eval.scm:
    619:8 19 (_ #(#(#(#<directory (guile-user) 129d140> #<<installer> name: 
newt init: #<procedure init ()> exit: #<procedure exit ()> exit-error: 
#<procedure exit-error (file key args)> fi…> …)) …))
   626:19 18 (_ #(#(#(#<directory (guile-user) 129d140> #<<installer> name: 
newt init: #<procedure init ()> exit: #<procedure exit ()> exit-error: 
#<procedure exit-error (file key args)> fi…> …)) …))
In ./gnu/installer/steps.scm:
    189:6 17 (run-installer-steps #:steps _ #:rewind-strategy _ #:menu-proc _)
In ice-9/boot-9.scm:
    829:9 16 (catch srfi-34 #<procedure 2ef1fc0 at 
./gnu/installer/steps.scm:144:7 ()> #<procedure 2e4d320 at 
./gnu/installer/steps.scm:144:7 (key c)> _)
In ./gnu/installer/steps.scm:
   182:21 15 (_)
In ice-9/eval.scm:
   293:34 14 (_ #(#(#<directory (guile-user) 129d140>) #<<installer> name: newt 
init: #<procedure init ()> exit: #<procedure exit ()> exit-error: #<procedure 
exit-error (file key args)> final-pa…>))
In ./gnu/installer/newt/locale.scm:
    225:3 13 (run-locale-page #:supported-locales _ #:iso639-languages _ 
#:iso3166-territories _)
In ./gnu/installer/steps.scm:
    189:6 12 (run-installer-steps #:steps _ #:rewind-strategy _ #:menu-proc _)
In ice-9/boot-9.scm:
    829:9 11 (catch srfi-34 #<procedure 2ef1c80 at 
./gnu/installer/steps.scm:144:7 ()> #<procedure 2e4d2d0 at 
./gnu/installer/steps.scm:144:7 (key c)> _)
In ./gnu/installer/steps.scm:
   182:21 10 (_)
In ./gnu/installer/newt/locale.scm:
     52:2  9 (run-language-page _ _)
In ice-9/boot-9.scm:
  1583:14  8 (setenv _ _)
In unknown file:
           7 (string-append "LANGUAGE" "=" #t)
In ice-9/boot-9.scm:
   751:25  6 (dispatch-exception 2 wrong-type-arg ("string-append" "Wrong type 
(expecting ~A): ~S" ("string" #t) (#t)))
In ice-9/eval.scm:
    619:8  5 (_ #(#(#<directory (guile-user) 129d140> #<<installer> name: newt 
init: #<procedure init ()> exit: #<procedure exit ()> exit-error: #<procedure 
exit-error (file key args)> final-…>) …))
    619:8  4 (_ #(#(#(#<directory (guile-user) 129d140> #<<installer> name: 
newt init: #<procedure init ()> exit: #<procedure exit ()> exit-error: 
#<procedure exit-error (file key args)> f…>) …) #))
In ice-9/ports.scm:
   462:17  3 (call-with-output-file _ _ #:binary _ #:encoding _)
In ice-9/eval.scm:
    619:8  2 (_ #(#(#<directory (guile-user) 129d140> wrong-type-arg 
("string-append" "Wrong type (expecting ~A): ~S" ("string" #t) (#t))) #<output: 
/tmp/last-installer-error 12>))
    159:9  1 (_ #(#(#<directory (guile-user) 129d140> wrong-type-arg 
("string-append" "Wrong type (expecting ~A): ~S" ("string" #t) (#t))) #<output: 
/tmp/last-installer-error 12>))
In unknown file:
           0 (make-stack #t)
ice-9/eval.scm:159:9: In procedure string-append: Wrong type (expecting 
string): #t
In ice-9/eval.scm:
    619:8 19 (_ #(#(#(#<directory (guile-user) 1962140> #<<installer> name: 
newt init: #<procedure init ()> exit: #<procedure exit ()> exit-error: 
#<procedure exit-error (file key args)> fi…> …)) …))
   626:19 18 (_ #(#(#(#<directory (guile-user) 1962140> #<<installer> name: 
newt init: #<procedure init ()> exit: #<procedure exit ()> exit-error: 
#<procedure exit-error (file key args)> fi…> …)) …))
In ./gnu/installer/steps.scm:
    189:6 17 (run-installer-steps #:steps _ #:rewind-strategy _ #:menu-proc _)
In ice-9/boot-9.scm:
    829:9 16 (catch srfi-34 #<procedure 378da00 at 
./gnu/installer/steps.scm:144:7 ()> #<procedure 3647be0 at 
./gnu/installer/steps.scm:144:7 (key c)> _)
In ./gnu/installer/steps.scm:
   182:21 15 (_)
In ice-9/eval.scm:
   293:34 14 (_ #(#(#<directory (guile-user) 1962140>) #<<installer> name: newt 
init: #<procedure init ()> exit: #<procedure exit ()> exit-error: #<procedure 
exit-error (file key args)> final-pa…>))
In ./gnu/installer/newt/locale.scm:
    225:3 13 (run-locale-page #:supported-locales _ #:iso639-languages _ 
#:iso3166-territories _)
In ./gnu/installer/steps.scm:
    189:6 12 (run-installer-steps #:steps _ #:rewind-strategy _ #:menu-proc _)
In ice-9/boot-9.scm:
    829:9 11 (catch srfi-34 #<procedure 378d6c0 at 
./gnu/installer/steps.scm:144:7 ()> #<procedure 3647b90 at 
./gnu/installer/steps.scm:144:7 (key c)> _)
In ./gnu/installer/steps.scm:
   182:21 10 (_)
In ./gnu/installer/newt/locale.scm:
     52:2  9 (run-language-page _ _)
In ice-9/boot-9.scm:
  1583:14  8 (setenv _ _)
In unknown file:
           7 (string-append "LANGUAGE" "=" #t)
In ice-9/boot-9.scm:
   751:25  6 (dispatch-exception 2 wrong-type-arg ("string-append" "Wrong type 
(expecting ~A): ~S" ("string" #t) (#t)))
In ice-9/eval.scm:
    619:8  5 (_ #(#(#<directory (guile-user) 1962140> #<<installer> name: newt 
init: #<procedure init ()> exit: #<procedure exit ()> exit-error: #<procedure 
exit-error (file key args)> final-…>) …))
    619:8  4 (_ #(#(#(#<directory (guile-user) 1962140> #<<installer> name: 
newt init: #<procedure init ()> exit: #<procedure exit ()> exit-error: 
#<procedure exit-error (file key args)> f…>) …) #))
In ice-9/ports.scm:
   462:17  3 (call-with-output-file _ _ #:binary _ #:encoding _)
In ice-9/eval.scm:
    619:8  2 (_ #(#(#<directory (guile-user) 1962140> wrong-type-arg 
("string-append" "Wrong type (expecting ~A): ~S" ("string" #t) (#t))) #<output: 
/tmp/last-installer-error 12>))
    159:9  1 (_ #(#(#<directory (guile-user) 1962140> wrong-type-arg 
("string-append" "Wrong type (expecting ~A): ~S" ("string" #t) (#t))) #<output: 
/tmp/last-installer-error 12>))
In unknown file:
           0 (make-stack #t)
ice-9/eval.scm:159:9: In procedure string-append: Wrong type (expecting 
string): #t