Parse the Map Settings field in the load scenario modal (#1032)

The Map Settings block parsed values.mapGenSettings, so filling in only
Map Settings failed with "undefined" is not valid JSON and the modal
would not submit, while filling in both sent the map gen settings JSON
to Factorio as --map-settings.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

packages/web_ui/src/components/LoadScenarioModal.tsx

@@ -44,7 +44,7 @@ export default function LoadScenarioModal(props: LoadScenarioModalProps) {
 		}
 		if (values.mapSettings && values.mapSettings.trim()) {
 			try {
-				mapSettings = JSON.parse(values.mapGenSettings);
+				mapSettings = JSON.parse(values.mapSettings);
 			} catch (err: any) {
 				form.setFields([{ name: "mapSettings", errors: [err.message] }]);
 				return;