Function returning it's argument or checking for nullptr

I would like to loop on a vector and filter out all the non-nullpointer elements. I'm looking for either an std function that checks for something being a nullptr or an std function that actually returns whatever is passed to it (like std::forward), since a nullpointer would evaluate to false.

std::copy_if(dynamicObjects.begin(), dynamicObjects.end(),
    std::back_inserter(existingObjects), 
    std::is_pointer<ObjectType*>); // This does not compile

std::copy_if(dynamicObjects.begin(), dynamicObjects.end(),
    std::back_inserter(existingObjects), 
    std::forwad<ObjectType*>); // This does not compile either

std::copy_if(dynamicObjects.begin(), dynamicObjects.end(),
    std::back_inserter(existingObjects), 
    [] (const auto a) { return a; } ); // This is awkward