Disable the right panel when the app asks us to

Currently this is only used in the GroupView and for forwarding messages.

src/components/structures/MatrixChat.js

@@ -177,7 +177,7 @@ export default createReactClass({
             collapseLhs: false,
             leftDisabled: false,
             middleDisabled: false,
-            rightDisabled: false,
+            // the right panel's disabled state is tracked in its store.
 
             version: null,
             newVersion: null,
@@ -660,7 +660,7 @@ export default createReactClass({
                 this.setState({
                     leftDisabled: payload.leftDisabled || payload.sideDisabled || false,
                     middleDisabled: payload.middleDisabled || false,
-                    rightDisabled: payload.rightDisabled || payload.sideDisabled || false,
+                    // We don't track the right panel being disabled here - it's tracked in the store.
                 });
                 break;
             }

src/components/structures/RoomDirectory.js

@@ -108,20 +108,9 @@ module.exports = createReactClass({
                 ),
             });
         });
-
-        // dis.dispatch({
-        //     action: 'panel_disable',
-        //     sideDisabled: true,
-        //     middleDisabled: true,
-        // });
     },
 
     componentWillUnmount: function() {
-        // dis.dispatch({
-        //     action: 'panel_disable',
-        //     sideDisabled: false,
-        //     middleDisabled: false,
-        // });
         if (this.filterTimeout) {
             clearTimeout(this.filterTimeout);
         }

src/stores/RightPanelStore.js

@@ -39,6 +39,8 @@ const GROUP_PHASES = Object.keys(RIGHT_PANEL_PHASES).filter(k => k.startsWith("G
 export default class RightPanelStore extends Store {
     static _instance;
 
+    _inhibitUpdates = false;
+
     constructor() {
         super(dis);
 
@@ -107,7 +109,12 @@ export default class RightPanelStore extends Store {
     }
 
     __onDispatch(payload) {
-        if (payload.action !== 'set_right_panel_phase') return;
+        if (payload.action === 'panel_disable') {
+            this._inhibitUpdates = payload.rightDisabled || payload.sideDisabled || false;
+            return;
+        }
+
+        if (payload.action !== 'set_right_panel_phase' || this._inhibitUpdates) return;
 
         const targetPhase = payload.phase;
         if (!RIGHT_PANEL_PHASES[targetPhase]) {