fix: 代码生成器多次调用报错。

mybatis-flex-codegen/src/main/java/com/mybatisflex/codegen/template/impl/EnjoyTemplate.java

@@ -45,12 +45,11 @@ public class EnjoyTemplate implements ITemplate {
                 e.addSharedStaticMethod(StringUtil.class);
                 e.setSourceFactory(new FileAndClassPathSourceFactory());
             });
-        }
-        this.engine = engine;
-
             // 以下配置将支持 user.girl 表达式去调用 user 对象的 boolean isGirl() 方法
             Engine.addFieldGetterToFirst(new FieldGetters.IsMethodFieldGetter());
         }
+        this.engine = engine;
+    }
 
     @Override
     public void generate(Map<String, Object> params, String templateFilePath, File generateFile) {