Description:
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for assign_dim, EG(error_zval) results NULL

but for assign_obj, it doesn't, which makes nothing, and also maybe make the EG(error_zval) altered.

Test script:
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<?php
$obj = unserialize('O:1:"A":0:{}');
var_dump($obj);
var_dump($obj->prop .= 0);

$arr = array(PHP_INT_MAX=>0);
var_dump($arr[] .= 0);

Expected result:
----------------
NULL
NULL

Actual result:
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string (1) "0"
NULL