Description:
------------
It crashes only with xdebug enabled on PHP 7.3.24-3+ubuntu18.04.1+deb.sury.org+1 

If I replace anonymous functions with regular functions or methods (like [$this, 'callbackEnv']) then php_yaml_check_callbacks (https://github.com/php/pecl-file_formats-yaml/blob/2.1.0/yaml.c#L305) doesn't crash.

Test script:
---------------
$data = \yaml_parse_file(
    $file,
    0,
    $ndocs,
    [
        '!env'  => function ($str) {
        },
        '!path' => function ($str) {
        },
    ]
);

Expected result:
----------------
No segfault :)

Actual result:
--------------
Program terminated with signal SIGSEGV, Segmentation fault.
#0  php_yaml_check_callbacks (callbacks=<optimized out>, callbacks=<optimized out>) at /tmp/pear/temp/yaml/yaml.c:305
305	/tmp/pear/temp/yaml/yaml.c: No such file or directory.
(gdb) bt
#0  php_yaml_check_callbacks (callbacks=<optimized out>, callbacks=<optimized out>) at /tmp/pear/temp/yaml/yaml.c:305
#1  0x00007f9fa33dd0b4 in zif_yaml_parse_file (execute_data=<optimized out>, return_value=0x7f9fb5a1eac0) at /tmp/pear/temp/yaml/yaml.c:415
#2  0x00007f9fb5266485 in xdebug_execute_internal (current_execute_data=0x7f9fb5a1eb90, return_value=0x7f9fb5a1eac0) at ./build-7.3/src/base/base.c:466
#3  0x0000563d30ea40df in ?? ()
#4  0x0000563d310dceb6 in execute_ex ()
#5  0x00007f9fb5265afc in xdebug_execute_ex (execute_data=0x7f9fb5a1e840) at ./build-7.3/src/base/base.c:380
#6  0x0000563d30ea3d29 in ?? ()
#7  0x0000563d310dceb6 in execute_ex ()