check on roomId instead of room

Author: toger5

src/components/views/voip/CallPreview.tsx

@@ -118,8 +118,8 @@ export default class CallPreview extends React.Component<IProps, IState> {
         this.roomStoreToken = RoomViewStore.addListener(this.onRoomViewStoreUpdate);
         this.dispatcherRef = dis.register(this.onAction);
         MatrixClientPeg.get().on(CallEvent.RemoteHoldUnhold, this.onCallRemoteHold);
-        const room = MatrixClientPeg.get().getRoom(this.state.roomId);
-        if (room) {
+        if (this.state.roomId) {
+            const room = MatrixClientPeg.get().getRoom(this.state.roomId);
             WidgetLayoutStore.instance.on(WidgetLayoutStore.emissionForRoom(room), this.updateCalls);
         }
     }
@@ -142,11 +142,11 @@ export default class CallPreview extends React.Component<IProps, IState> {
         if (newRoomId === oldRoomId) return;
         // The WidgetLayoutStore observer always tracks the currently viewed Room,
         // so we don't end up with multiple observers and know what observer to remove on unmount
-        const newRoom = MatrixClientPeg.get().getRoom(newRoomId);
-        const oldRoom = MatrixClientPeg.get().getRoom(oldRoomId);
-        if (oldRoom) {
+        if (oldRoomId) {
+            const oldRoom = MatrixClientPeg.get().getRoom(oldRoomId);
             WidgetLayoutStore.instance.off(WidgetLayoutStore.emissionForRoom(oldRoom), this.updateCalls);
         }
+        const newRoom = MatrixClientPeg.get().getRoom(newRoomId);
         WidgetLayoutStore.instance.on(WidgetLayoutStore.emissionForRoom(newRoom), this.updateCalls);
 
         const [primaryCall, secondaryCalls] = getPrimarySecondaryCallsForPip(newRoomId);