The coat of arms of the reigning Roman Pontiff signifies the active pastoral leadership of the one elected. The chair of Saint Peter is occupied.
When the Pontiff dies, we say that the chair is empty —sede vacante. This period of time in the church when it does not have is visualized by the Sede Vacante Coat of Arms (shown above).
During the Sede vacante period the Pope is mourned, there are the funeral rites and then the preparation for the Mass of the Holy Spirit and election of a new head and father of the Church.
What do we see on the sede vacante coat of arms? Red Umbrella (Ombrellino): A traditional symbol of the Church in waiting. Half-open, it shows the pope is absent—but the Church still stands.
Crossed Keys of St. Peter: Gold and silver keys represent the authority Christ gave to St. Peter. Even without a pope, that authority continues.
Hence the optic is an important reminder that the Church didn’t or doesn’t collapse without a pope—she waits, prays, and trusts the Holy Spirit.