Call of Overloaded Functions is Ambiguous

Question

I'm getting the error call of overloaded function is ambiguous and I understand it's because the compiler can't differentiate between them, but is there a way to work around this while maintaining the same parameters? I have to use the declarations I've provided below and it's confusing me as to how I can use them both if I met with this error every time.

I've shortened my code to show the constructors that are posing the issue.

ErrorMessage.h

class ErrorMessage {
        char* message_; //pointer that holds the address of the message stored in current object
    public:
        ErrorMessage();
        explicit ErrorMessage(const char* errorMessage = nullptr); //receive address of a C-style nullterminate string holding an error message
}

ErrorMessage.cpp

namespace sict {

ErrorMessage::ErrorMessage() {
    message_ = nullptr;
}

ErrorMessage::ErrorMessage(const char* errorMessage) {
    if(errorMessage == nullptr) {
        message_ = nullptr;
    }
    else {
        message(errorMessage);
    }
    const char* ErrorMessage::message() const {
        return message_;
    }
}

Answer 1

Just remove the constructor which takes no parameters. The second constructor already does everything the first constructor does.

If it receives a nullptr, it tests it and sets the local variable, if not it continues with its logic. The first constructor is completely superfluous.