bug#29879: guix package search error.

[Fis Trivial]

* Version

$: guix pull

Updating from Git repository at 'https://git.savannah.gnu.org/git/guix.git'...
Building from Git commit 6b681ddda0f965d4163fbeb4b34520c91bd01f5d...
Guix already up to date



* Error and backtrace:

$: guix package --search=mutt

Backtrace:
In guix/ui.scm:
  1474:12 19 (run-guix-command _ . _)
In ice-9/boot-9.scm:
    837:9 18 (catch _ _ #<procedure 7f9d36ed4258 at guix/ui.scm:533…> …)
    837:9 17 (catch _ _ #<procedure 7f9d36ed4270 at guix/ui.scm:633…> …)
In guix/scripts/package.scm:
   912:10 16 (_)
    770:9 15 (process-query _)
In ice-9/boot-9.scm:
    837:9 14 (catch _ _ #<procedure 7f9d33b8f3c0 at guix/scripts/pa…> …)
In guix/scripts/package.scm:
   772:24 13 (_)
   249:17 12 (find-packages-by-description _)
In guix/discovery.scm:
    137:3 11 (fold-module-public-variables _ _ _)
In guix/combinators.scm:
    45:26 10 (fold2 #<procedure 407e780 at guix/discovery.scm:137:1…> …)
    45:26  9 (fold2 #<procedure 3182c00 at guix/discovery.scm:138:1…> …)
In guix/discovery.scm:
   140:33  8 (_ #<package address@hidden gnu/packages/finance.s…> …)
In guix/scripts/package.scm:
   250:34  7 (_ #<package address@hidden gnu/packages/finance.s…> …)
In srfi/srfi-1.scm:
   466:18  6 (fold #<procedure 2c20700 at guix/ui.scm:1143:8 (metri…> …)
In guix/ui.scm:
  1146:13  5 (_ _ 0)
  1025:23  4 (texi->plain-text _)
In texinfo.scm:
  1131:22  3 (parse _)
   979:31  2 (loop #<input: string 28ad1c0> (*fragment*) _ _ _)
   868:21  1 (visit example #<input: string 28ad1c0> #f ((para #) #))
   675:23  0 (complete-start-command _ #<input: string 28ad1c0>)

texinfo.scm:675:23: In procedure complete-start-command:
texinfo.scm:675:23: Throw to key `parser-error' with args `(#<input: string 
28ad1c0> "@-command didn't expect more args" example (".com --connect"))'.