Don't crash immediately if the room directory chunk is null/empty
Don't crash immediately if the room directory chunk is null/empty

Fixes https://github.com/vector-im/riot-web/issues/12197
matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk