fix(core): App should not crash with a custom rest endpoint (#5911)

fixes #5880

packages/cli/src/commands/start.ts

@@ -144,6 +144,7 @@ export class Start extends BaseCommand {
 	private async generateStaticAssets() {
 		// Read the index file and replace the path placeholder
 		const n8nPath = config.getEnv('path');
+		const restEndpoint = config.getEnv('endpoints.rest');
 		const hooksUrls = config.getEnv('externalFrontendHooksUrls');
 
 		let scriptsString = '';
@@ -167,6 +168,7 @@ export class Start extends BaseCommand {
 				];
 				if (filePath.endsWith('index.html')) {
 					streams.push(
+						replaceStream('{{REST_ENDPOINT}}', restEndpoint, { ignoreCase: false }),
 						replaceStream(closingTitleTag, closingTitleTag + scriptsString, {
 							ignoreCase: false,
 						}),