fix invalid syntax code generated from an empty schema

Author: mizdra

src/__snapshots__/code-generator.test.ts.snap

@@ -59,7 +59,6 @@ exports[`generateCode > generates code when empty typeInfos is passed 1`] = `
 } from '@mizdra/graphql-codegen-typescript-fabbrica/helper';
 import type {
   Maybe,
-,
 } from './types';
 
 export * from '@mizdra/graphql-codegen-typescript-fabbrica/helper';

src/code-generator.ts

@@ -4,17 +4,16 @@ import type { ObjectTypeInfo, TypeInfo } from './schema-scanner.js';
 function generatePreludeCode(config: Config, typeInfos: TypeInfo[]): string {
   const joinedTypeNames = typeInfos
     .filter(({ type }) => type === 'object')
-    .map(({ name }) => `  ${name}`)
-    .join(',\n');
+    .map(({ name }) => `  ${name},\n`)
+    .join('');
   const code = `
 import {
   type DefineTypeFactoryInterface${config.nonOptionalDefaultFields ? 'Required' : ''},
   defineTypeFactory,
 } from '@mizdra/graphql-codegen-typescript-fabbrica/helper';
 import type {
   Maybe,
-${joinedTypeNames},
-} from '${config.typesFile}';
+${joinedTypeNames}} from '${config.typesFile}';
 
 export * from '@mizdra/graphql-codegen-typescript-fabbrica/helper';
   `.trim();