[LyX/master] Fixup b0c102cfb: make it possible to select medskip as parskip

[Jean-Marc Lasgouttes]

Le 29/10/2021 à 16:50, Jürgen Spitzmüller a écrit :
> Am Freitag, dem 29.10.2021 um 16:17 +0200 schrieb Jean-Marc Lasgouttes:
>> commit 5c055034c2076160bcb6ea7ae6d42de694cc2ca7
>> Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
>> Date:   Fri Oct 29 16:38:29 2021 +0200
>>
>>      Fixup b0c102cfb: make it possible to select medskip as parskip
>>      
>>      Some new parskip possibilities had been added, but the check for
>>      custom length index had not bee updated.
>>      
>>      This code is very fragile.
> 
> It would be better to use (string) data here rather than index.

Please do it along with the other stuff of this bug, I am a dummy when 
it comes dialog code.

JMarc