Can't use raster Unique values symbolgogy for Integer rasters with a single value of 1.

[cratcliff]

What is the bug or the crash?

Raster Paletted/Unique values renderer and Singleband pseudocolor does not work when a single unique value of 1 is used with any integer data types.

Steps to reproduce the issue

1. Load or create a single band geotif with data type of integer or unsigned integer and constant pixel value of 1.

2. Apply symbology using Paletted/Unique values. Clicking Classify does nothing, and you have to add the value manually.

Versions

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QGIS version	3.28.2-Firenze	QGIS code revision	b47e00b
Qt version	5.15.3
Python version	3.9.5
GDAL/OGR version	3.6.1
PROJ version	9.1.1
EPSG Registry database version	v10.076 (2022-08-31)
GEOS version	3.11.1-CAPI-1.17.1
SQLite version	3.39.4
PDAL version	2.4.3
PostgreSQL client version	unknown
SpatiaLite version	5.0.1
QWT version	6.1.6
QScintilla2 version	2.13.1
OS version	Windows 10 Version 2009
Active Python plugins
db_manager	0.1.20
processing	2.12.99

QGIS version 3.28.2-Firenze QGIS code revision [b47e00b](https://github.com/qgis/QGIS/commit/b47e00ba601) Qt version 5.15.3 Python version 3.9.5 GDAL/OGR version 3.6.1 PROJ version 9.1.1 EPSG Registry database version v10.076 (2022-08-31) GEOS version 3.11.1-CAPI-1.17.1 SQLite version 3.39.4 PDAL version 2.4.3 PostgreSQL client version unknown SpatiaLite version 5.0.1 QWT version 6.1.6 QScintilla2 version 2.13.1 OS version Windows 10 Version 2009

Active Python plugins
db_manager
0.1.20
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

Problem also exists in QGIS 3.26.3.

Using python commands doesn't work either and QgsPalettedRasterRenderer.classDataFromRaster(raster_layer.dataProvider(), 1 ) returns an empty list.

[elpaso]

it actually crashes on Linux/master