Description:
------------
Segmentation fault is triggered due to null pointer dereference in zend_fetch_dimension_address_read() with the given php script. 

Address sanitizer shows:
 

AddressSanitizer:DEADLYSIGNAL
=================================================================
==4575==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000010 (pc 0x0000016c426a bp 0x7fff1318b790 sp 0x7fff1318af60 T0)
==4575==The signal is caused by a READ memory access.
==4575==Hint: address points to the zero page.
    #0 0x16c4269 in zend_fetch_dimension_address_read php-7.2.34/Zend/zend_execute.c:1800:7
    #1 0x16c4269 in zend_fetch_dimension_address_read_R_slow php-7.2.34/Zend/zend_execute.c:1855
    #2 0x1379a9b in ZEND_FETCH_DIM_R_SPEC_CV_CONST_HANDLER php-7.2.34/Zend/zend_vm_execute.h:36219:4
    #3 0x11f2aad in execute_ex php-7.2.34/Zend/zend_vm_execute.h:59767:7
    #4 0x11f3e92 in zend_execute php-7.2.34/Zend/zend_vm_execute.h:63804:2
    #5 0xfd7e9b in zend_execute_scripts php-7.2.34/Zend/zend.c:1498:4
    #6 0xd4a23a in php_execute_script php-7.2.34/main/main.c:2599:14
    #7 0x171d99f in do_cli php-7.2.34/sapi/cli/php_cli.c:1011:5
    #8 0x171ab8b in main php-7.2.34/sapi/cli/php_cli.c:1403:18
    #9 0x7fafaac66b96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310
    #10 0x432279 in _start (php-7.2.34/sapi/cli/php+0x432279)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV php-7.2.34/Zend/zend_execute.c:1800:7 in zend_fetch_dimension_address_read
==4575==ABORTING


Test script:
---------------
<?php

$my_var = null;
set_error_handler(function() use(&$my_var) {
    $my_var = 0;
});

$my_var[] .= "xyz";
var_dump($my_var);

$my_var = null;
$my_var[0][0][0] .= "xyz";
var_dump($my_var);

$my_var = nual;
$my_var["foo"] . "xyz";
var_dump($my_var);

$my_Var = null;
$my_var["foo"]["bar"]["baz"] .= "xyz";
var_dump($my_var);

?>

Expected result:
----------------
No seg fault.

Actual result:
--------------
Segmentation fault.