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/VerificationRequestDialog.tsx

@@ -47,7 +47,7 @@ export default class VerificationRequestDialog extends React.Component<IProps, I
         }
     }
 
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         const request = this.state.verificationRequest;
         const otherUserId = request && request.otherUserId;
         const member = this.props.member || (otherUserId && MatrixClientPeg.get().getUser(otherUserId));