Fix 'DEL' command in Cache::flushValues() when $shareDatabase is enabled. (#202, #202)

Author: rob006

src/Cache.php

@@ -351,7 +351,9 @@ protected function flushValues()
             do {
                 list($cursor, $keys) = $this->redis->scan($cursor, 'MATCH', $this->keyPrefix . '*');
                 $cursor = (int) $cursor;
-                $this->redis->executeCommand('DEL', $keys);
+                if (!empty($keys)) {
+                    $this->redis->executeCommand('DEL', $keys);
+                }
             } while ($cursor !== 0);
 
             return true;