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/TextualBody.tsx

@@ -562,7 +562,7 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
         return <span className="mx_EventTile_pendingModeration">{`(${text})`}</span>;
     }
 
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         if (this.props.editState) {
             const isWysiwygComposerEnabled = SettingsStore.getValue("feature_wysiwyg_composer");
             return isWysiwygComposerEnabled ? (