delegates_qobject_large_array.qml regression

Regression visible between 5.6 and 5.9

Test: /benchmarks/auto/creation/quick/delegates_qobject_large_array.qml
Grafana: https://testresults.qt.io/grafana/dashboard/db/qmlbench-branches?panelId=152&fullscreen&orgId=1&var-suite=creation%2Fquick&var-suite=creation%2Fquick.validators&var-benchmark=All&var-branch=v5.9.0&var-branch=5.9&var-branch=5.6&var-hardwareId=eskil_linux_tx1&from=now-1y&to=now