style lost when you modify expression on geometry generator

[crocovert]

Hello

Describe the bug
I used a categorized style based on a geometry generator (polygons in my example).
When I changed modify the expression of the geometry generator (for example a value) the style is lost ans all polygons are black

How to Reproduce
Load a polygon layer
In style choose categorized (but the bug exists for graduated styles too) for example the following expression ($id %2). choose diffretent styles for odd and even rows

In the geometry editor choose an expression (ex: buffer(geometry,5000) )

Then, if your modify the expression of the geometry editor (ex: buffer(geometry,600)) the style will be lost and you will have only black circles

QGIS and OS versions

Version de QGIS	3.10.0-A Coruña	Révision du code	6c816b4
Compilé avec Qt	5.11.2	Utilisant Qt	5.11.2
Compilé avec GDAL/OGR	2.4.1	Utilisé avec GDAL/OGR	2.4.1
Compilé avec GEOS	3.8.0-CAPI-1.13.1	Utilisé avec GEOS	3.8.0-CAPI-1.13.1
Compiled against SQLite	3.29.0	Running against SQLite	3.29.0
Version du client PostgreSQL	11.5	Version de SpatiaLite	4.3.0
Version de QWT	6.1.3	Version de QScintilla2	2.10.8
Compilé avec PROJ	5.2.0	Fonctionne avec PROJ	Rel. 5.2.0, September 15th, 2018
OS Version	Windows 10 (10.0)
Extensions Python actives	french_locator_filter; mmqgis; networks; nominatim; pluginbuilder3; Qgis2threejs; QuickOSM; quick_map_services; db_manager; MetaSearch; processing

Thank you

[nyalldawson]

Duplicate of #38377