(gdb) bt full
#0  QQmlVMEMetaObject::metaCall (this=0x555557c97460, o=<optimized out>, c=QMetaObject::ReadProperty, _id=4,
    a=0x7fffff7ff100) at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/qml/qml/qqmlvmemetaobject.cpp:596
        id = 4
#1  0x00007ffff4d4c379 in ReadAccessor::Indirect (property=..., n=0x0, output=0x7fffff7ff0e0, object=0x555557c958b0)
    at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/qml/jsruntime/qv4qobjectwrapper.cpp:125
        args = {0x7fffff7ff0e0, 0x0}
#2  LoadProperty<ReadAccessor::Indirect> (v4=v4@entry=0x555555932d70, object=object@entry=0x555557c958b0, property=...,
    notifier=0x0) at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/qml/jsruntime/qv4qobjectwrapper.cpp:160
        rv = 0x0
        scope = {engine = 0x555555932d70, mark = 0x7fffd115b728}
#3  0x00007ffff4d50abd in QV4::QObjectWrapper::getProperty (engine=engine@entry=0x555555932d70, object=0x555557c958b0,
    property=0x7fffc08b4198, captureRequired=captureRequired@entry=true)
    at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/qml/jsruntime/qv4qobjectwrapper.cpp:386
        ep = <optimized out>
#4  0x00007ffff4d5167a in QV4::QObjectWrapper::getQmlProperty (this=0x7fffd115b720, qmlContext=0x555557c95570,
    name=0x7fffd115b6e0, revisionMode=QV4::QObjectWrapper::CheckRevision, hasProperty=0x7fffff7ff340,
    includeImports=<optimized out>)
    at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/qml/jsruntime/qv4qobjectwrapper.cpp:324
        local = {<QQmlPropertyRawData> = {{propType = 0,
              propTypeName = 0x555500000000 <error: Cannot access memory at address 0x555500000000>}, {notifyIndex = -1,
              arguments = 0x564259d5ffffffff}, {{revision = 0, metaObjectOffset = -1, {{valueTypeFlags = 65534,
                    valueTypePropType = 65535, valueTypeCoreIndex = 62432}, {overrideIndexIsProperty = 0,
                    overrideIndex = -1}}}, {accessors = 0xfffffffeffff0000}}, coreIndex = -1, flags = 0}, <No data fields>}
        result = 0x7fffc08b4198
        ddata = <optimized out>
        this = 0x7fffd115b720
        includeImports = false
        hasProperty = 0x7fffff7ff340
        revisionMode = QV4::QObjectWrapper::CheckRevision
        name = 0x7fffd115b6e0
        qmlContext = 0x555557c95570
#5  0x00007ffff4d5196f in QV4::QObjectWrapper::getQmlProperty (engine=engine@entry=0x555555932d70,
    qmlContext=qmlContext@entry=0x555557c95570, object=<optimized out>, name=name@entry=0x7fffd115b6e0,
    revisionMode=revisionMode@entry=QV4::QObjectWrapper::CheckRevision, hasProperty=hasProperty@entry=0x7fffff7ff340)
    at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/qml/jsruntime/qv4qobjectwrapper.cpp:411
No locals.
#6  0x00007ffff4df7d03 in QV4::QmlContextWrapper::get (m=<optimized out>, name=0x7fffd115b6e0, hasProperty=0x7fffff7ff420)
    at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/qml/qml/qqmlcontextwrapper.cpp:230
        hasProp = true
        properties = <optimized out>
---Type <return> to continue, or q <return> to quit---
        resource = <optimized out>
        scope = {engine = 0x555555932d70, mark = 0x7fffd115b710}
        hasProp = false
        result = <optimized out>
        context = 0x555557c95570
        expressionContext = 0x55555784d180

        scopeObject = 0x0

#7  0x00007ffff4cd4bc6 in QV4::Object::get (hasProperty=0x7fffff7ff420, name=0x7fffd115b6e0, this=<optimized out>)
    at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/qml/jsruntime/qv4object_p.h:306
No locals.
#8  QV4::ExecutionContext::getProperty (this=<optimized out>, name=0x7fffd115b6e0)
    at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/qml/jsruntime/qv4context.cpp:469
        qml = <optimized out>
        hasProperty = false
        scope = {engine = 0x555555932d70, mark = 0x7fffd115b6e8}
        v = {ptr = 0x7fffd115b6e8}
        hasWith = <optimized out>
        hasCatchScope = <optimized out>
        ctx = {ptr = 0x7fffd115b6f0}
        n = <optimized out>


#9  0x00007ffff4d639b0 in QV4::Runtime::getActivationProperty (engine=0x555555932d70, nameIndex=<optimized out>)
    at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/qml/jsruntime/qv4runtime.cpp:724
        scope = {engine = 0x555555932d70, mark = 0x7fffd115b6e0}
        name = {ptr = 0x7fffd115b6e0}
#10 0x00007fff29af8099 in ?? ()