bug#56864: qutebrowser: wrap-qt-process-path phase wrong type to string-append

[Lars-Dominik Braun]

Hi Maxim,

> Yep, that did it.
> 
> Fixed in aea756ea3312ba7e8229804492ba12001c8de568.

this does not fix the build of lyx and twinkle for me, which both fail at 
'qt-wrap:

---snip---
starting phase `qt-wrap'
error: in phase 'qt-wrap': uncaught exception:
wrong-type-arg "substring" "Wrong type argument in position ~A (expecting ~A): 
~S" (1 "string" #f) (#f)
phase `qt-wrap' failed after 0.0 seconds
Backtrace:
           9 (primitive-load "/gnu/store/gm47sv2ndfg906vkdr68nbv7zsi…")
In guix/build/gnu-build-system.scm:
    906:2  8 (gnu-build #:source _ #:outputs _ #:inputs _ #:phases . #)
In ice-9/boot-9.scm:
  1752:10  7 (with-exception-handler _ _ #:unwind? _ # _)
In srfi/srfi-1.scm:
    634:9  6 (for-each #<procedure 7ffff0b45020 at guix/build/gnu-b…> …)
In ice-9/boot-9.scm:
  1752:10  5 (with-exception-handler _ _ #:unwind? _ # _)
In guix/build/gnu-build-system.scm:
   927:23  4 (_)
In guix/build/qt-utils.scm:
   148:22  3 (wrap-all-qt-programs #:inputs _ #:outputs _ #:qtbase _ …)
In unknown file:
           2 (string-drop #f 44)
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 substring: Wrong type argument in position 1 (expecting string): #f
---snap---

Maybe a different incarnation of the same issue?

Lars