qmltest::ListView() flood of "Object destroyed during incubation"

~/qt/qt5-build/qtdeclarative/tests/auto/qmltest$ make check
/Users/liangqi/qt/qt5-build/qtdeclarative/tests/auto/qmltest/target_wrapper.sh  ./tst_qmltest 
********* Start testing of qmltest *********
Config: Using QtTest library 5.6.1, Qt 5.6.1 (x86_64-little_endian-lp64 shared (dynamic) debug build; by Clang 7.3.0 (clang-703.0.31) (Apple))
...
QWARN  : qmltest::ListView::test_asyncListViewLoader() file:///Users/liangqi/qt/qt5/qtdeclarative/tests/auto/qmltest/listview/data/asynclistviewloader.qml: Object destroyed during incubation
...
QWARN  : qmltest::ListView::test_asyncListViewLoader() file:///Users/liangqi/qt/qt5/qtdeclarative/tests/auto/qmltest/listview/data/asynclistviewloader.qml: Object destroyed during incubation
PASS   : qmltest::ListView::test_asyncListViewLoader()
QWARN  : qmltest::ListView::test_asyncLoaderCurrentIndexChange() file:///Users/liangqi/qt/qt5/qtdeclarative/tests/auto/qmltest/listview/data/asyncloadercurrentindex.qml: Object destroyed during incubation
...
QWARN  : qmltest::ListView::test_asyncLoaderCurrentIndexChange() file:///Users/liangqi/qt/qt5/qtdeclarative/tests/auto/qmltest/listview/data/asyncloadercurrentindex.qml: Object destroyed during incubation
QSYSTEM: qmltest::ListView::test_asyncLoaderCurrentIndexChange() Maximum amount of warnings exceeded. Use -maxwarnings to override.
PASS   : qmltest::ListView::test_asyncLoaderCurrentIndexChange()
...
********* Finished testing of qmltest *********