QString in std::vector triggers gcc's -Wnull-dereference

#include <vector>

#include <QString>

int main()
 {
    std::vector<QString> const a\{""};

    auto const t = a;

    return t.size() == 0;
 }

/tmp % g++ -std=c++17 -Werror=null-dereference -I/usr/include/qt5/QtCore -I/usr/include/qt5 -fPIC -c -O1 t.cpp
In file included from /usr/include/qt5/QtCore/qglobal.h:105,
 from /usr/include/qt5/QtCore/qchar.h:43,
 from /usr/include/qt5/QtCore/qstring.h:48,
 from /usr/include/qt5/QtCore/QString:1,
 from t.cpp:3:
/usr/include/qt5/QtCore/qstring.h: In function 'int main()':
/usr/include/qt5/QtCore/qcompilerdetection.h:1129:26: error: null pointer dereference [-Werror=null-dereference]
 1129 | # define Q_DECL_NOEXCEPT noexcept
 | ^~~~~~~~
/usr/include/qt5/QtCore/qcompilerdetection.h:1139:25: note: in expansion of macro 'Q_DECL_NOEXCEPT'
 1139 | # define Q_DECL_NOTHROW Q_DECL_NOEXCEPT
 | ^~~~~~~~~~~~~~~
/usr/include/qt5/QtCore/qstring.h:957:47: note: in expansion of macro 'Q_DECL_NOTHROW'
 957 | inline QString::QString(const QString &other) Q_DECL_NOTHROW : d(other.d)
 | ^~~~~~~~~~~~~~
In file included from /usr/include/qt5/QtCore/QString:1,
 from t.cpp:3:
/usr/include/qt5/QtCore/qstring.h:957:73: error: null pointer dereference [-Werror=null-dereference]
 957 | inline QString::QString(const QString &other) Q_DECL_NOTHROW : d(other.d)
 | ^
cc1plus: some warnings being treated as errors