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/elements/crypto/VerificationQRCode.tsx

@@ -24,7 +24,7 @@ interface IProps {
 }
 
 export default class VerificationQRCode extends React.PureComponent<IProps> {
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         return (
             <QRCode
                 data={[{ data: this.props.qrCodeData.getBuffer(), mode: "byte" }]}