QtCharts: fix GCC 13-detected dangling element reference warning

QColorAxis::gradient() returns a QLinearGradient by value,
QGradient::stops() returns a QList<QGradientStop> by value, so storing
the reference returned by QList::operator[] is, strictly speaking,
dangling. In practice, it isn't because QList is COW and thus the
element is not going to be destroyed, but let's not depend on that
detail.

chartaxiselement.cpp:437:33: error: possibly dangling reference to a temporary [-Werror=dangling-reference]
chartaxiselement.cpp:437:71: note: the temporary was destroyed at the end of the full expression ‘QGradient::stops() const().QList<std::pair<double, QColor> >::operator[](((qsizetype)i))’

Change-Id: Ide4dbd0777a44ed0870efffd1739488e1958f814
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>
(cherry picked from commit 7ced4f03281c253be098c126b72457201a44d2a0)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/charts/axis/chartaxiselement.cpp b/src/charts/axis/chartaxiselement.cpp
index 1723ba29..bfabfa26 100644
--- a/src/charts/axis/chartaxiselement.cpp
+++ b/src/charts/axis/chartaxiselement.cpp
@@ -434,7 +434,7 @@ void ChartAxisElement::prepareColorScale(const qreal width, const qreal height)
             } else {
                 gradient = QLinearGradient(QPointF(0, 0), QPointF(0, height));
                 for (int i = colorAxis->gradient().stops().size() - 1; i >= 0; --i) {
-                    const auto &stop = colorAxis->gradient().stops()[i];
+                    auto stop = colorAxis->gradient().stops()[i];
                     gradient.setColorAt(1 - stop.first, stop.second);
                 }
             }