TreeModel: return default roleNames if source model is goneHEADdev

When shutting down a Quick application that uses TreeView and
HorizontalHeaderView, the model might get destroyed before the UI does.
In that case, we'd get a runtime warning that

The 'textRole' property contains a role that doesn't exist in the model:
"display". Check your model's roleNames() implementation

This is because QQmlTreeModelToTableModel implements roleNames() to
return an empty container if there is no model, which is the case here:
the model is destroyed, the QPointer holding it becomes nullptr, and the
framework wants to store the old roles to see if anything changes when a
new model is ultimately set. QHeaderDataProxyModel::roleNames() then
ends up emitting the warning that the textRole is not found in the
model.

The logical thing to do is to return the default QAIM::roleNames() when
there is no model, as done elsewhere.

Pick-to: 6.11
Change-Id: If0a1c8bc428b00605e7c8b9d708c4551ef86dc5c
Reviewed-by: Dilek Akcay <dilek.akcay@qt.io>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

0 files changed, 0 insertions, 0 deletions