I get a build error when updating fmit with

    guix upgrade fmit

It fails with

    phase `install' succeeded after 0.4 seconds
    starting phase `wrap-executable'
    error: in phase 'wrap-executable': uncaught exception:
    wrong-type-arg "string-append" "Wrong type (expecting ~A): ~S" ("string" #f) (#f)
    phase `wrap-executable' failed after 0.0 seconds
    Backtrace:
              14 (primitive-load "/gnu/store/k7dvw09nink46bbpls85bzw5560…")
    In guix/build/gnu-build-system.scm:
        906:2 13 (gnu-build #:source _ #:outputs _ #:inputs _ #:phases . #)
    In ice-9/boot-9.scm:
      1752:10 12 (with-exception-handler _ _ #:unwind? _ # _)
    In srfi/srfi-1.scm:
        634:9 11 (for-each #<procedure 7ffff0b66660 at guix/build/gnu-b…> …)
    In ice-9/boot-9.scm:
      1752:10 10 (with-exception-handler _ _ #:unwind? _ # _)
    In guix/build/gnu-build-system.scm:
       927:23  9 (_)
    In ice-9/eval.scm:
        619:8  8 (_ #(#(#(#<directory (guile-user) 7ffff1fd3c80>) # #) #))
        163:9  7 (_ #(#(#(#<directory (guile-user) 7ffff1fd3c80>) # #) #))
       174:20  6 (_ #(#(#(#<directory (guile-user) 7ffff1fd3c80>) # #) #))
       177:32  5 (lp (#<procedure 7ffff070c120 at ice-9/eval.scm:182:7 …>))
    In ice-9/boot-9.scm:
       222:29  4 (map1 ("qtbase" "qtmultimedia-5" "qtsvg-5"))
       222:17  3 (map1 ("qtmultimedia-5" "qtsvg-5"))
    In unknown file:
               2 (string-append #f "/lib/qt5/plugins")
    In ice-9/boot-9.scm:
      1685:16  1 (raise-exception _ #:continuable? _)
      1685:16  0 (raise-exception _ #:continuable? _)
    
    ice-9/boot-9.scm:1685:16: In procedure raise-exception:
    In procedure string-append: Wrong type (expecting string): #f
    

The full error-log is attached.

To reproduce you can use my manifest (also attached).

    guix package  --fallback -k -m ~/fluss-guix.manifest

Best wishes,
Arne