fix[group]handle_request reason empty

src/core/src/apis/group.ts

@@ -125,7 +125,7 @@ export class NTQQGroupApi {
           'seq': seq,  // 通知序列号
           'type': type,
           'groupCode': groupCode,
-          'postscript': reason || ''
+          'postscript': reason || ' ' // 仅传空值可能导致处理失败，故默认给个空格
         }
       });
   }

src/onebot11/action/group/SetGroupAddRequest.ts

@@ -9,7 +9,7 @@ const SchemaData = {
   properties: {
     flag: { type: 'string' },
     approve: { type: ['string', 'boolean'] },
-    reason: { type: 'string' }
+    reason: { type: 'string', nullable: true, }
   },
   required: ['flag'],
 } as const satisfies JSONSchema;