修复 issue top-think#468 db链式方法cache查询时判断和返回类型错误问题

src/db/PDOConnection.php

@@ -724,9 +724,10 @@ protected function pdoQuery(BaseQuery $query, $sql, bool $master = null): array
                 $key = $cacheItem->getKey();
 
                 $data = $this->cache->get($key);
-
-                if (null !== $data) {
+                if (gettype($data) !== 'boolean' && null !== $data) {
                     return $data;
+                } else {
+                    return [];
                 }
             }
         }