pure virtual method called terminate called without an active exception

Question

I have an issue. I am making a game where i check if a projectile is below the screen, if true i want to delete that object. My problem is that when the projectile actually goes below sceen my game crashes with the error:

pure virtual method called terminate called without an active exception

which i think is very wierd because my projectile class has nothing to do with a virtual method or abstract class. This is the update methods:

void GameScene::updateLogic() {
    if (projectile) {
        if (projectile -> position().y > 1200) {
            t1Turn = true;
            delete projectile;
        }
        else {
            projectile->update();
        }
    }
}

void GameScene::draw() {
    if (projectile) {
        projectile->draw(_window);
    }
}

The projectile pointer is set to nullptr in the constructor of the gamescene:

_p = nullptr;

The projectile class:

Projectile::Projectile(sf::Vector2f spawnPoint, sf::Vector2f initVel, Tank* target, bool& turn) : _spawnPoint(spawnPoint), _initVel(initVel), _target(target), _turn(turn) {}
Projectile::~Projectile(){}
void Projectile::update(){
   if (_collisionBox.intersects(_target->getBox())) {
       _target->removeHealth(20);
    }
    _elapsed = clock.getElapsedTime().asSeconds();
    _time += _elapsed;
    clock.restart();
    dx = (_initVel.x * _time);
    dy = (_initVel.y * _time + (1900*pow(_time, 2) / 2));
    _position = sf::Vector2f(_spawnPoint.x+dx, _spawnPoint.y+dy);
    _collisionBox = _projectileSprite.getGlobalBounds();
}

void Projectile::draw(sf::RenderWindow &window) {
    _projectileSprite.setPosition(_position);
    window.draw(_projectileSprite);
}

sf::Vector2f Projectile::position () {
    return _position;
}

The projectile inherits from a sprite class but thats about it:

class Projectile : Sprites {

It has no association with a pure virtual method...

EDIT: When running the debugger it breaks at:

void Projectile::draw(sf::RenderWindow &window) { window <incomplete type>
    _projectileSprite.setPosition(_position);
    window.draw(_projectileSprite); <--------------------
}

But how can window be of incomplete type? What has that to do with a virtual method which the original error message say?