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/SeshatResetDialog.tsx

@@ -22,7 +22,7 @@ import DialogButtons from "../elements/DialogButtons";
 import { IDialogProps } from "./IDialogProps";
 
 export default class SeshatResetDialog extends React.PureComponent<IDialogProps> {
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         return (
             <BaseDialog
                 hasCancel={true}