修复3.0书源的搜索url为空时无法导入书源的bug

app/src/main/java/io/legado/app/help/storage/OldRule.kt

@@ -19,7 +19,7 @@ object OldRule {
             source = GSON.fromJsonObject<BookSource>(json.trim())
         }
         runCatching {
-            if (source == null || source?.searchUrl.isNullOrBlank()) {
+            if (source == null || source?.ruleToc.isNullOrBlank()) {
                 source = BookSource().apply {
                     val jsonItem = jsonPath.parse(json.trim())
                     bookSourceUrl = jsonItem.readString("bookSourceUrl") ?: ""