Truth value of QgsLayerTreeNode changes between QGIS3 and QGIS4 #65755

What is the bug or the crash?

In QGIS3, the truth value of a QgsLayerTreeNode (layer or group) was always True.

This allowed to write the following

layer_id = "my_id"
node = QgsProject.instance().layerTreeRoot().findLayer(layer_id)
if node:
    # Process node
    ...

In QGIS4 the truth value of a QgsLayerTreeLayer is always False, and True only for QgsLayerTreeGroup with child nodes.

Steps to reproduce the issue

QGIS4

>>> bool(QgsLayerTreeLayer(""))
False

QGIS3

>>> bool(QgsLayerTreeLayer(""))
True

Versions

QGIS 3.44.8 vs QGIS 4.0.0

Supported QGIS version

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

New profile

• I tried with a new QGIS profile

No Duplicate of the Issue

• I have verified that there are no existing issues raised related to my problem.

Additional context

No response