Description:
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When I add the same server to pool and use persistance connection it will generate segmentation fault for getExtendedStats

Reproduce code:
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    $memcache_obj = new Memcache;
    $memcache_obj->addServer('localhost', 11211);
    $memcache_obj->addServer('localhost', 11211);
    //$memcache_obj->addServer('failed_host', 11211);
    
    $stats = $memcache_obj->getExtendedStats();
    print_r($stats);

Expected result:
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No segmentation fault

Actual result:
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segmentation fault