Description:
------------
Last week, I found a CI failure[1] of pecl/zookeeper. I thought it would be compatibility problem because I turned on PHP-7.3 in .travis.yml.

When I looked into that issue, I found it's weird because the crash point was in the PHP src, and it only crashed when I passed an empty array to the function provided pass-by-ref var.

So I wrote a small ext to reproduce that:

```c
PHP_FUNCTION(caseone_test1)
{
        zval *param;

        if (zend_parse_parameters(ZEND_NUM_ARGS(), "z", &param) == FAILURE) {
                return;
        }

        if (param) {
                ZVAL_DEREF(param);
        }

        if (Z_TYPE_P(param) != IS_ARRAY) {
                array_init(param);
        }

        add_assoc_long_ex(param, ZEND_STRL("foo"), 0);
}
```

```php
$param = [];
caseone_test1($param);
```

```gdb
#0  0x000056193020c64e in zend_hash_real_init_mixed_ex (ht=ht@entry=0x5619305fe220 <zend_empty_array>) at /usr/src/debug/php-7.3.1/Zend/zend_hash.c:131
#1  zend_hash_real_init_mixed (ht=ht@entry=0x5619305fe220 <zend_empty_array>) at /usr/src/debug/php-7.3.1/Zend/zend_hash.c:260
#2  0x000056193020db88 in _zend_hash_str_add_or_update_i (flag=1, pData=0x7fffbb8834d0, h=9223372037048267657, len=3, str=0x7ff29e4b7d93 "foo", ht=0x5619305fe220 <zend_empty_array>)
    at /usr/src/debug/php-7.3.1/Zend/zend_hash.c:746
#3  zend_hash_str_update (ht=ht@entry=0x5619305fe220 <zend_empty_array>, str=str@entry=0x7ff29e4b7d93 "foo", len=len@entry=3, pData=pData@entry=0x7fffbb8834d0)
    at /usr/src/debug/php-7.3.1/Zend/zend_hash.c:854
#4  0x00005619302021a8 in zend_symtable_str_update (pData=0x7fffbb8834d0, len=3, str=0x7ff29e4b7d93 "foo", ht=0x5619305fe220 <zend_empty_array>)
    at /usr/src/debug/php-7.3.1/Zend/zend_hash.h:498
#5  add_assoc_long_ex (arg=<optimized out>, key=key@entry=0x7ff29e4b7d93 "foo", key_len=key_len@entry=3, n=n@entry=0) at /usr/src/debug/php-7.3.1/Zend/zend_API.c:1359
#6  0x00007ff29e4b7c7c in zif_caseone_test1 (execute_data=<optimized out>, return_value=<optimized out>) at /root/php-7.3.1/ext/caseone/caseone.c:29
#7  0x000056193028b2f9 in ZEND_DO_ICALL_SPEC_RETVAL_UNUSED_HANDLER () at /usr/src/debug/php-7.3.1/Zend/zend_vm_execute.h:645
#8  execute_ex (ex=0x5619305fe220 <zend_empty_array>) at /usr/src/debug/php-7.3.1/Zend/zend_vm_execute.h:55414
#9  0x000056193028f3a3 in zend_execute (op_array=op_array@entry=0x7ff2a267d2a0, return_value=0x0, return_value@entry=0x7ff2a267d3e0)
    at /usr/src/debug/php-7.3.1/Zend/zend_vm_execute.h:60834
#10 0x0000561930200622 in zend_execute_scripts (type=type@entry=8, retval=0x7ff2a267d3e0, retval@entry=0x0, file_count=-1570648016, file_count@entry=3)
    at /usr/src/debug/php-7.3.1/Zend/zend.c:1568
#11 0x00005619301a05d0 in php_execute_script (primary_file=primary_file@entry=0x7fffbb885b80) at /usr/src/debug/php-7.3.1/main/main.c:2630
#12 0x0000561930291892 in do_cli (argc=3, argv=0x561930f3f960) at /usr/src/debug/php-7.3.1/sapi/cli/php_cli.c:997
#13 0x000056193000121b in main (argc=3, argv=0x561930f3f960) at /usr/src/debug/php-7.3.1/sapi/cli/php_cli.c:1389
```

When I changed the former PHP script to :
```php
$param = '';
caseone_test1($param);
```
or
```php
$param = [0];
caseone_test1($param);
```
, they worked fine.

This issue can only be reproduced under Linux.
I'm not sure it's a bug or not, so I turned to you guys for help.

System info:
```shell
uname -a
Linux 93a912e38b29 4.9.125-linuxkit #1 SMP Fri Sep 7 08:20:28 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
```
```shell
cat /etc/redhat-release
CentOS Linux release 7.6.1810 (Core)
```


[1] https://api.travis-ci.org/v3/job/484167428/log.txt