Unexpected behavior using multiedit support for relation editor

What is the bug or the crash?

Multiedit support for relation editor fails in the context that is described.

Steps to reproduce the issue

Create a SpatiaLite with this schema or use this template.

CREATE TABLE t1_parent (
    id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, 
    name TEXT
);

SELECT AddGeometryColumn('t1_parent', 'geom', 32628, 'POLYGON', 'XY');
SELECT CreateSpatialIndex('t1_parent', 'geom');

CREATE TABLE t1_child (
    id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, 
    name TEXT,
    parent_id INTEGER REFERENCES t1_parent(id) DEFERRABLE INITIALLY DEFERRED
);

Activate Automatically create transaction groups where possible and Evaluate default values on provider side project options.
Set up a relation between tables.

Configure t1_parent form.

Create 3 parents with 2 childs each one. After start an editing session, select the 3 parent features and press "Modify the Attributes of All Selected Features Simultaneously" you will see:

If you clic on "Add child feature" this error happens.

Versions

QGIS version 3.24.2-Tisler QGIS code revision 13c1a028 Qt version 5.15.2 Python version 3.9.5 GDAL/OGR version 3.4.2 PROJ version 9.0.0 EPSG Registry database version v10.054 (2022-02-13) GEOS version 3.10.2-CAPI-1.16.0 SQLite version 3.38.1 PDAL version 2.3.0 PostgreSQL client version unknown SpatiaLite version 5.0.1 QWT version 6.1.3 QScintilla2 version 2.11.5 OS version Windows 10 Version 2009

Active Python plugins db_manager 0.1.20 grassprovider 2.12.99 MetaSearch 0.3.6 processing 2.12.99 sagaprovider 2.12.99

Supported QGIS version

[X] I'm running a supported QGIS version according to the roadmap.

New profile

[X] I tried with a new QGIS profile

Additional context

Multi edit support for relation editor was developed by @domi4484. See changelog for QGIS 3.24.

qgis / QGIS