Method try_set_existing

ImGuiFileDialog.h:299–306

    }

    bool try_set_existing(T vKey) {
        if (exist(vKey)) {
            auto row     = m_Dico.at(vKey);
            m_Array[row] = vKey;
            return true;
        }
        return false;
    }

    bool exist(const std::string& vKey) const {
        return (m_Dico.find(vKey) != m_Dico.end());