ui-file-based (combo-box-containing-) forms are not working in QGIS 3.34 any longer

[koenigherford]

What is the bug or the crash?

Since QGIS 3.34. combo-boxes ore not working properly when using value-relations. They are empty instead of filled by the expected data.

Steps to reproduce the issue

1.1)
Create a new project with a (geometry)-layer (and a "type"-field, which shall be populated by a value-relation) and
1.2)
Create a second layer which is used as the ("types"-)data-layer to populate the value-relation-widget.

Create a ui-file with a combo-box and name it the same way like the geometry-layer-field "type".

Go to layer-properties of geometry-layer and select under "attibutes-form "provide-ui-file" and select new ui-file from step 2)

Digitize a new feature-> Combo-Box is empty in QGIS 3.34

Open project in 3.28-> Combo-box is poulated in QGIS 3.28

Versions

<style> </style>

QGIS version	3.34.1-Prizren	QGIS code revision	1339274
Qt version	5.15.3
Python version	3.9.5
GDAL/OGR version	3.8.0
PROJ version	9.3.0
EPSG Registry database version	v10.094 (2023-08-08)
GEOS version	3.12.1-CAPI-1.18.1
SQLite version	3.41.1
PDAL version	2.6.0
PostgreSQL client version	15.2
SpatiaLite version	5.1.0
QWT version	6.1.6
QScintilla2 version	2.13.4
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

QGIS version 3.34.1-Prizren QGIS code revision [1339274](https://github.com/qgis/QGIS/commit/133927424d) Qt version 5.15.3 Python version 3.9.5 GDAL/OGR version 3.8.0 PROJ version 9.3.0 EPSG Registry database version v10.094 (2023-08-08) GEOS version 3.12.1-CAPI-1.18.1 SQLite version 3.41.1 PDAL version 2.6.0 PostgreSQL client version 15.2 SpatiaLite version 5.1.0 QWT version 6.1.6 QScintilla2 version 2.13.4 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

Supported QGIS version

• I'm running a supported QGIS version according to the roadmap.

New profile

• I tried with a new QGIS profile

Additional context

No response

[koenigherford]

Test-UI and Test-file attached
ui_test.zip