Conform more code to strict null checking (#10167)

* Conform more code to strict null checking

* Delint

* Iterate PR based on feedback

src/settings/SettingsStore.ts

@@ -437,7 +437,7 @@ export default class SettingsStore {
         level: SettingLevel,
         roomId: string | null,
         calculatedValue: any,
-        calculatedAtLevel: SettingLevel,
+        calculatedAtLevel: SettingLevel | null,
     ): any {
         let resultingValue = calculatedValue;