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/messages/MVideoBody.tsx

@@ -232,7 +232,7 @@ export default class MVideoBody extends React.PureComponent<IBodyProps, IState>
         return this.showFileBody && <MFileBody {...this.props} showGenericPlaceholder={false} />;
     };
 
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         const content = this.props.mxEvent.getContent();
         const autoplay = SettingsStore.getValue("autoplayVideo");