Deselect message history message when topic selection changes

Fixes #93

app/src/reducers/index.ts

@@ -5,6 +5,7 @@ import { GlobalState, globalState } from './Global'
 import { publishReducer, PublishState } from './Publish'
 import { Record } from 'immutable'
 import { settingsReducer, SettingsState } from './Settings'
+import { sidebarReducer, SidebarState } from './Sidebar'
 import { treeReducer, TreeState } from './Tree'
 
 export interface AppState {
@@ -12,6 +13,7 @@ export interface AppState {
   tree: TreeState
   settings: Record<SettingsState>,
   publish: PublishState
+  sidebar: SidebarState,
   connection: ConnectionState
   connectionManager: ConnectionManagerState
 }
@@ -19,6 +21,7 @@ export interface AppState {
 export default combineReducers({
   globalState,
   publish: publishReducer,
+  sidebar: sidebarReducer,
   connection: connectionReducer,
   settings: settingsReducer,
   tree: treeReducer,