Hello/Hi/Greetings,

My Piwigo albums seem to be running fine, however I have recently had problems with the Admin login section. After I have logged in, the page I arrive at is split in half across the centre. The top half is just plain blue, and on the lefthand side is a single column of print:

Administration
     Home
     Photos
    Albums
    Plugins
    users
    Tools
    Configuration
Saved
Tools
View As
Theme
language   etc etc

Below the central line is the normal header-bar for the gallery, and below that are my normal gallery images for the albums.
I can access the Administration link at the far right side of the header bar. It all works ok but it is very untidy and I found it rather disturbing when the section first showed signs of breaking-up.

Has something happened to the configuration or themes, or something else? I am running the newest version of Piwigo and, until a month or so ago, this split-screen issue wasn't there.

(Copy here your environment details, found on your Piwigo page [Administration > Tools > Maintenance])
Environment
Piwigo 2.10.2
Operating system: Linux
PHP: 7.3.23 (Show info) [2020-11-28 12:23:20]
MySQL: 8.0.21-cll-lve [2020-11-28 12:23:20]
Graphics Library: External ImageMagick 6.9.10-68

Piwigo URL: http://