Memory leak when signal containing QJsonObject parameter is emitted from C++ and handled in QML

==29589== 4,378,600 bytes in 100,000 blocks are definitely lost in loss record 203 of 203
==29589==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==29589==    by 0x6973359: QArrayData::allocate(unsigned long, unsigned long, unsigned long, QFlags<QArrayData::AllocationOption>) (qarraydata.cpp:101)
==29589==    by 0x6A9B900: QTypedArrayData<unsigned short>::allocate(unsigned long, QFlags<QArrayData::AllocationOption>) (qarraydata.h:223)
==29589==    by 0x6A8943C: QString::fromLatin1_helper(char const*, int) (qstring.cpp:4400)
==29589==    by 0x694DFEB: QString::fromLatin1(char const*, int) (qstring.h:493)
==29589==    by 0x6C91193: QJsonPrivate::Latin1String::toString() const (qjson_p.h:426)
==29589==    by 0x6C9021E: QJsonPrivate::Entry::key() const (qjson_p.h:623)
==29589==    by 0x6C8FE32: QJsonObject::keyAt(int) const (qjsonobject.cpp:1050)
==29589==    by 0x6558BE4: QJsonObject::const_iterator::key() const (qjsonobject.h:160)
==29589==    by 0x6556EF3: QV4::JsonObject::fromJsonObject(QV4::ExecutionEngine*, QJsonObject const&) (qv4jsonobject.cpp:1003)
==29589==    by 0x66C4165: QV8Engine::fromVariant(QVariant const&) (qv8engine.cpp:295)
==29589==    by 0x65BD6F9: QV4::QObjectSlotDispatcher::impl(int, QtPrivate::QSlotObjectBase*, QObject*, void**, bool*) (qv4qobjectwrapper.cpp:795)