[BUG] Invalid memory read in zim_Phalcon_Cache_Backend_Memcached_flush

[ghost]

See https://travis-ci.org/sjinks/cphalcon/jobs/13313682#L532

==18131== Invalid read of size 8
==18131== at 0x83EC93: zend_hash_move_forward_ex (/tmp/php-build/source/5.3.26/Zend/zend_hash.c:1088)
==18131== by 0x11D26C59: zim_Phalcon_Cache_Backend_Libmemcached_flush (/home/travis/build/sjinks/cphalcon/ext/cache/backend/libmemcached.c:646)
==18131== by 0x11BAB627: phalcon_execute_internal (/home/travis/build/sjinks/cphalcon/ext/phalcon.c:385)
==18131== by 0x8B7B06: zend_do_fcall_common_helper_SPEC (/tmp/php-build/source/5.3.26/Zend/zend_vm_execute.h:324)
==18131== by 0x85731D: execute (/tmp/php-build/source/5.3.26/Zend/zend_vm_execute.h:107)
==18131== by 0x8225B9: zend_call_function (/tmp/php-build/source/5.3.26/Zend/zend_execute_API.c:969)
==18131== by 0x65D829: zim_reflection_method_invokeArgs (/tmp/php-build/source/5.3.26/ext/reflection/php_reflection.c:2753)
==18131== by 0x11BAB627: phalcon_execute_internal (/home/travis/build/sjinks/cphalcon/ext/phalcon.c:385)
==18131== by 0x8B7B06: zend_do_fcall_common_helper_SPEC (/tmp/php-build/source/5.3.26/Zend/zend_vm_execute.h:324)
==18131== by 0x85731D: execute (/tmp/php-build/source/5.3.26/Zend/zend_vm_execute.h:107)
==18131== by 0x83155B: zend_execute_scripts (/tmp/php-build/source/5.3.26/Zend/zend.c:1259)
==18131== by 0x7D04C8: php_execute_script (/tmp/php-build/source/5.3.26/main/main.c:2316)
==18131== Address 0x176466c0 is 32 bytes inside a block of size 76 free'd
==18131== at 0x4C2A82E: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==18131== by 0x83DB53: zend_hash_del_key_or_index (/tmp/php-build/source/5.3.26/Zend/zend_hash.c:505)
==18131== by 0x11BB4D61: phalcon_array_unset (/home/travis/.phpenv/versions/5.3.26/include/php/Zend/zend_hash.h:353)
==18131== by 0x11D26BEA: zim_Phalcon_Cache_Backend_Libmemcached_flush (/home/travis/build/sjinks/cphalcon/ext/cache/backend/libmemcached.c:653)
==18131== by 0x11BAB627: phalcon_execute_internal (/home/travis/build/sjinks/cphalcon/ext/phalcon.c:385)
==18131== by 0x8B7B06: zend_do_fcall_common_helper_SPEC (/tmp/php-build/source/5.3.26/Zend/zend_vm_execute.h:324)
==18131== by 0x85731D: execute (/tmp/php-build/source/5.3.26/Zend/zend_vm_execute.h:107)
==18131== by 0x8225B9: zend_call_function (/tmp/php-build/source/5.3.26/Zend/zend_execute_API.c:969)
==18131== by 0x65D829: zim_reflection_method_invokeArgs (/tmp/php-build/source/5.3.26/ext/reflection/php_reflection.c:2753)
==18131== by 0x11BAB627: phalcon_execute_internal (/home/travis/build/sjinks/cphalcon/ext/phalcon.c:385)
==18131== by 0x8B7B06: zend_do_fcall_common_helper_SPEC (/tmp/php-build/source/5.3.26/Zend/zend_vm_execute.h:324)
==18131== by 0x85731D: execute (/tmp/php-build/source/5.3.26/Zend/zend_vm_execute.h:107)
==18131==