Conform more code to strict null checking (#10167)

* Conform more code to strict null checking

* Delint

* Iterate PR based on feedback

test/components/views/settings/DevicesPanel-test.tsx

@@ -74,7 +74,7 @@ describe("<DevicesPanel />", () => {
 
         const toggleDeviceSelection = (container: HTMLElement, deviceId: string) =>
             act(() => {
-                const checkbox = container.querySelector(`#device-tile-checkbox-${deviceId}`);
+                const checkbox = container.querySelector(`#device-tile-checkbox-${deviceId}`)!;
                 fireEvent.click(checkbox);
             });
 
@@ -204,7 +204,7 @@ describe("<DevicesPanel />", () => {
 
             // close the modal without submission
             act(() => {
-                const modalCloseButton = document.querySelector('[aria-label="Close dialog"]');
+                const modalCloseButton = document.querySelector('[aria-label="Close dialog"]')!;
                 fireEvent.click(modalCloseButton);
             });
 

test/components/views/settings/tabs/user/PreferencesUserSettingsTab-test.tsx

@@ -49,6 +49,7 @@ describe("PreferencesUserSettingsTab", () => {
             const client = MatrixClientPeg.get();
             jest.spyOn(client, "isVersionSupported").mockImplementation(async (version: string) => {
                 if (version === "v1.4") return val;
+                return false;
             });
         };
 
@@ -61,8 +62,12 @@ describe("PreferencesUserSettingsTab", () => {
             };
         };
 
-        const expectSetValueToHaveBeenCalled = (name: string, roomId: string, level: SettingLevel, value: boolean) =>
-            expect(SettingsStore.setValue).toHaveBeenCalledWith(name, roomId, level, value);
+        const expectSetValueToHaveBeenCalled = (
+            name: string,
+            roomId: string | undefined,
+            level: SettingLevel,
+            value: boolean,
+        ) => expect(SettingsStore.setValue).toHaveBeenCalledWith(name, roomId, level, value);
 
         describe("with server support", () => {
             beforeEach(() => {