Improve typescript null checking in places (#10073 (#10073

* Improve typescript null checking in places

* Iterate

* Fix Timer.ts

src/stores/OwnProfileStore.ts

@@ -50,8 +50,8 @@ export class OwnProfileStore extends AsyncStoreWithClient<IState> {
         // round-trip after the client is ready, and we often load widgets in that time, and we'd
         // and up passing them an incorrect display name
         super(defaultDispatcher, {
-            displayName: window.localStorage.getItem(KEY_DISPLAY_NAME),
-            avatarUrl: window.localStorage.getItem(KEY_AVATAR_URL),
+            displayName: window.localStorage.getItem(KEY_DISPLAY_NAME) || undefined,
+            avatarUrl: window.localStorage.getItem(KEY_AVATAR_URL) || undefined,
         });
     }
 

src/stores/ReadyWatchingStore.ts

@@ -25,7 +25,7 @@ import { IDestroyable } from "../utils/IDestroyable";
 import { Action } from "../dispatcher/actions";
 
 export abstract class ReadyWatchingStore extends EventEmitter implements IDestroyable {
-    protected matrixClient: MatrixClient;
+    protected matrixClient: MatrixClient | null = null;
     private dispatcherRef: string | null = null;
 
     public constructor(protected readonly dispatcher: Dispatcher<ActionPayload>) {
@@ -42,7 +42,7 @@ export abstract class ReadyWatchingStore extends EventEmitter implements IDestro
         }
     }
 
-    public get mxClient(): MatrixClient {
+    public get mxClient(): MatrixClient | null {
         return this.matrixClient; // for external readonly access
     }
 

src/stores/UIStore.ts

@@ -21,7 +21,7 @@ export enum UI_EVENTS {
 }
 
 export default class UIStore extends EventEmitter {
-    private static _instance: UIStore = null;
+    private static _instance: UIStore | null = null;
 
     private resizeObserver: ResizeObserver;
 
@@ -58,7 +58,7 @@ export default class UIStore extends EventEmitter {
         }
     }
 
-    public getElementDimensions(name: string): DOMRectReadOnly {
+    public getElementDimensions(name: string): DOMRectReadOnly | undefined {
         return this.uiElementDimensions.get(name);
     }
 
@@ -68,7 +68,7 @@ export default class UIStore extends EventEmitter {
     }
 
     public stopTrackingElementDimensions(name: string): void {
-        let trackedElement: Element;
+        let trackedElement: Element | undefined;
         this.trackedUiElements.forEach((trackedElementName, element) => {
             if (trackedElementName === name) {
                 trackedElement = element;

src/stores/spaces/flattenSpaceHierarchy.ts

@@ -66,7 +66,7 @@ export const flattenSpaceHierarchyWithCache =
         useCache = true,
     ): Set<string> => {
         if (useCache && cache.has(spaceId)) {
-            return cache.get(spaceId);
+            return cache.get(spaceId)!;
         }
         const result = flattenSpaceHierarchy(spaceEntityMap, spaceDescendantMap, spaceId);
         cache.set(spaceId, result);