Почему вылетает ошибка: C:\DEVELOPMENT\Qt5.12.9\5.12.9\mingw73_64\include\QtCore\qvector.h:687: ошибка: cannot bind non-const lvalue reference of type 'AltIdent&' to an rvalue of type 'std::remove_ref

Всем доброго времени суток.
Помогите разобраться, что я делаю не так?
Есть несколько классов. Вот они:

class AltIdent
{
public:
    AltIdent();
    AltIdent(const AltIdent &);
    AltIdent(PartNumber partnumber, ManufacturerCode manufacturercode);
    ~AltIdent(){}

    PartNumber getPartNumberObject() const;
    void setPartNumberObject(const PartNumber &value);

    ManufacturerCode getManufacturerCodeObject() const;
    void setManufacturerCodeObject(const ManufacturerCode &value);

bool isEmpty();
    AltIdent *isNull();
    AltIdent operator= (AltIdent &altident);

private:
    PartNumber partNumberObject;
    ManufacturerCode manufacturerCodeObject;
};

#include "altident.h"

AltIdent::AltIdent()
{

}

AltIdent::AltIdent(const AltIdent &altident)
{
    partNumberObject = altident.getPartNumberObject();
    manufacturerCodeObject = altident.getManufacturerCodeObject();
}

AltIdent::AltIdent(PartNumber partnumnber, ManufacturerCode manufacturercode):
    partNumberObject(partnumnber), manufacturerCodeObject(manufacturercode)
{

}

PartNumber AltIdent::getPartNumberObject() const
{
    return partNumberObject;
}

void AltIdent::setPartNumberObject(const PartNumber &value)
{
    partNumberObject = value;
}

ManufacturerCode AltIdent::getManufacturerCodeObject() const
{
    return manufacturerCodeObject;
}

void AltIdent::setManufacturerCodeObject(const ManufacturerCode &value)
{
    manufacturerCodeObject = value;
}

bool AltIdent::isEmpty()
{
    if(isNull() != nullptr){
        if(!getPartNumberObject().isEmpty()){
            return false;
        }
        if(!getManufacturerCodeObject().isEmpty()){
            return false;
        }
    }
    return true;
}

AltIdent *AltIdent::isNull()
{
    AltIdent *altIdent = this;
    if(altIdent != nullptr){
        return this;
    }
    return nullptr;
}

AltIdent AltIdent::operator=(AltIdent &altident)
{
    return *new AltIdent(altident.getPartNumberObject(), altident.getManufacturerCodeObject());
}

class PartNumber
{
public:
    PartNumber();
    PartNumber(const PartNumber &);
    PartNumber(const QString &partNumberStr, const QMap<QString, QString> &attrMap);
    ~PartNumber(){}

    QString getPartNumberValue() const;
    void setPartNumberValue(const QString &value);

    QMap<QString, QString> getPartNumberAttrMap() const;
    void setPartNumberAttrMap(const QMap<QString, QString> &value);

    bool isEmpty();
    PartNumber *isNull();

private:
    QString partNumberValue;
    QMap<QString, QString> partNumberAttrMap;
};

#include "partnumber.h"

PartNumber::PartNumber()
{

}

PartNumber::PartNumber(const PartNumber &partnumber)
{
    partNumberValue = partnumber.getPartNumberValue();
    partNumberAttrMap = partnumber.getPartNumberAttrMap();
}

PartNumber::PartNumber(const QString &partNumberStr, const QMap<QString, QString> &attrMap) :
    partNumberValue(partNumberStr), partNumberAttrMap(attrMap)
{

}

QMap<QString, QString> PartNumber::getPartNumberAttrMap() const
{
    return partNumberAttrMap;
}

void PartNumber::setPartNumberAttrMap(const QMap<QString, QString> &value)
{
    partNumberAttrMap = value;
}

QString PartNumber::getPartNumberValue() const
{
    return partNumberValue;
}

void PartNumber::setPartNumberValue(const QString &value)
{
    partNumberValue = value;
}

bool PartNumber::isEmpty()
{
    if(isNull() != nullptr && !partNumberValue.isEmpty()){
        return false;
    }
    return true;
}

PartNumber *PartNumber::isNull()
{
    PartNumber *partNumber = this;
    if(partNumber != nullptr){
        return this;
    }
    return nullptr;
}

class ManufacturerCode
{
public:
    ManufacturerCode();
    ManufacturerCode(const ManufacturerCode &);
    ManufacturerCode(const QString &manufacturerCode, const QMap<QString, QString> &attrMap);
    ~ManufacturerCode(){}

    QMap<QString, QString> getManufacturerCodeAttrMap() const;
    void setManufacturerCodeAttrMap(const QMap<QString, QString> &value);

    QString getManufacturerCodeValue() const;
    void setManufacturerCodeValue(const QString &value);

    QDomElement manufacturerCodeToXml(QDomDocument &domdocument);
    void manufacturerCodeFromXml(QDomElement &domelement);

    bool isEmpty();
    ManufacturerCode *isNull();

private:
    QString manufacturerCodeValue;
    QMap<QString, QString> manufacturerCodeAttrMap;

};

#include "manufacturercode.h"

ManufacturerCode::ManufacturerCode()
{

}

ManufacturerCode::ManufacturerCode(const ManufacturerCode &manufacturercode)
{
    *this = manufacturercode;
}

ManufacturerCode::ManufacturerCode(const QString &manufacturerCode,const QMap<QString, QString> &attrMap) :
    manufacturerCodeValue(manufacturerCode), manufacturerCodeAttrMap(attrMap)
{

}

QMap<QString, QString> ManufacturerCode::getManufacturerCodeAttrMap() const
{
    return manufacturerCodeAttrMap;
}

void ManufacturerCode::setManufacturerCodeAttrMap(const QMap<QString, QString> &value)
{
    manufacturerCodeAttrMap = value;
}

QString ManufacturerCode::getManufacturerCodeValue() const
{
    return manufacturerCodeValue;
}

void ManufacturerCode::setManufacturerCodeValue(const QString &value)
{
    manufacturerCodeValue = value;
}

bool ManufacturerCode::isEmpty()
{
    if(isNull() != nullptr && !manufacturerCodeValue.isEmpty()){
        return false;
    }
    return true;
}

ManufacturerCode *ManufacturerCode::isNull()
{
    ManufacturerCode *manufacturerCode = this;
    if(manufacturerCode != nullptr){
        return this;
    }
    return nullptr;
}

В другом файле сосздаю вектор:

    AltIdent m_altIdentOrigin;
    AltIdent m_altIdentCurrent;
    QVector<AltIdent> m_altIdentList;

На кнопку QPushButton повесил обработчик, который должен по индексу присвоить переменной m_altIdentCurrent элемент массива

void AltIdentGroupWidget::previewItem(const int &index)
{
    m_altIdentOrigin = m_altIdentList.at(index);
}

Но при компиляции получаю следующие ошибки:
1. C:\DEVELOPMENT\Qt5.12.9\5.12.9\mingw73_64\include\QtCore\qvector.h:687: ошибка: cannot bind non-const lvalue reference of type 'AltIdent&' to an rvalue of type 'std::remove_reference ::type {aka AltIdent}'
d->end() = qMove(copy);
2. C:\DEVELOPMENT\Qt5.12.9\5.12.9\mingw73_64\include\QtCore\qvector.h:693: ошибка: binding reference of type 'AltIdent&' to 'const AltIdent' discards qualifiers
d->end() = t;
~~~~~~~~~~^~~

И я не могу разобраться, что я делаю не так?
Помогите разобраться, пожалуйста.