Keep memberlist until rightpanel is closed

- This should make switching between memberlist and
  member-details panel smoother for large rooms

Signed-off-by: RMidhunSuresh <rmidhunsuresh@gmail.com>

src/domain/session/rightpanel/MemberListViewModel.js

@@ -7,7 +7,6 @@ export class MemberListViewModel extends ViewModel {
     constructor(options) {
         super(options);
         const list = options.members;
-        this.track(() => list.release());
 
         const powerLevelsObservable = options.powerLevelsObservable;
         this.track(powerLevelsObservable.subscribe(() => { /*resort based on new power levels here*/ }));

src/domain/session/rightpanel/RightPanelViewModel.js

@@ -7,16 +7,20 @@ export class RightPanelViewModel extends ViewModel {
     constructor(options) {
         super(options);
         this._room = options.room;
+        this._members = null;
         this._setupNavigation();
     }
 
     get activeViewModel() { return this._activeViewModel; }
 
     async _getMemberListArguments() {
-        const members = await this._room.loadMemberList();
+        if (!this._members) {
+            this._members = await this._room.loadMemberList();
+            this.track(() => this._members.release());
+        }
         const room = this._room;
         const powerLevelsObservable = await this._room.observePowerLevels();
-        return {members, powerLevelsObservable, mediaRepository: room.mediaRepository};
+        return {members: this._members, powerLevelsObservable, mediaRepository: room.mediaRepository};
     }
 
     async _getMemberDetailsArguments() {