书源校验：搜索结果为空时才把发现的结果给books

app/src/main/java/io/legado/app/service/CheckSourceService.kt

@@ -164,7 +164,7 @@ class CheckSourceService : BaseService() {
                         }
                     } else {
                         source.removeGroup("发现失效")
-                        books = exploreBooks
+                        if (books.isEmpty()) books = exploreBooks
                     }
                 }
             }