Conform more of the code base to strict null checking (#10147)

* Conform more of the code base to strict null checking

* More strict fixes

* More strict work

* Fix missing optional type

* Iterate

src/components/views/dialogs/security/RestoreKeyBackupDialog.tsx

@@ -308,7 +308,7 @@ export default class RestoreKeyBackupDialog extends React.PureComponent<IProps,
         }
     }
 
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         const backupHasPassphrase =
             this.state.backupInfo &&
             this.state.backupInfo.auth_data &&