Fix the call preview when not in same room as the call
Fix the call preview when not in same room as the call

Classic failure of an ES6 map also being a regular object :(

Fixes https://github.com/vector-im/element-web/issues/15343

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