Refactor generator to prevent duplicate reloading

src/app/components/generator/PreviewPanel.tsx

@@ -9,7 +9,7 @@ import { BiomeSourcePreview, DecoratorPreview, DensityFunctionPreview, NoisePrev
 export const HasPreview = ['dimension', 'worldgen/density_function', 'worldgen/noise', 'worldgen/noise_settings', 'worldgen/configured_feature', 'worldgen/placed_feature']
 
 type PreviewPanelProps = {
-	model: DataModel | null,
+	model: DataModel | undefined,
 	version: VersionId,
 	id: string,
 	shown: boolean,

src/app/components/generator/SourcePanel.tsx

@@ -52,8 +52,8 @@ interface Editor {
 
 type SourcePanelProps = {
 	name: string,
-	model: DataModel | null,
-	blockStates: BlockStateRegistry | null,
+	model: DataModel | undefined,
+	blockStates: BlockStateRegistry | undefined,
 	doCopy?: number,
 	doDownload?: number,
 	doImport?: number,

src/app/components/generator/Tree.tsx

@@ -7,8 +7,8 @@ import type { BlockStateRegistry, VersionId } from '../../services'
 
 type TreePanelProps = {
 	version: VersionId,
-	model: DataModel | null,
-	blockStates: BlockStateRegistry | null,
+	model: DataModel | undefined,
+	blockStates: BlockStateRegistry | undefined,
 	onError: (message: string) => unknown,
 }
 export function Tree({ version, model, blockStates, onError }: TreePanelProps) {