Fix double free

[remicollet]

GDB backtrace using PHP 8.6.0beta3

(gdb) bt
#0  0x00007ffff6c81a2c in __pthread_kill_implementation () from /lib64/libc.so.6
#1  0x00007ffff6c27bde in raise () from /lib64/libc.so.6
#2  0x00007ffff6c0f6d0 in abort () from /lib64/libc.so.6
#3  0x0000555555432a18 in zend_mm_panic (message=message@entry=0x555555a9adf0 "zend_mm_heap corrupted (double free)")
    at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/Zend/zend_alloc.c:392
#4  0x000055555543320a in zend_mm_free_small (heap=<optimized out>, ptr=<optimized out>, bin_num=<optimized out>)
    at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/Zend/zend_alloc.c:1502
#5  zend_mm_free_heap (heap=<optimized out>, ptr=<optimized out>) at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/Zend/zend_alloc.c:1601
#6  _efree (ptr=<optimized out>) at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/Zend/zend_alloc.c:2892
#7  0x00007ffff7faeeea in php_xziop_close (stream=<optimized out>, close_handle=1) at /work/GIT/pecl-and-ext/xz-codemasher/xz_fopen_wrapper.c:321
#8  0x00005555557a1661 in php_stream_free (stream=<optimized out>, close_options=3) at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/main/streams/streams.c:367
#9  0x00007ffff7faf21a in php_stream_xzopen (wrapper=wrapper@entry=0x0, path=<optimized out>, mode_pass=mode_pass@entry=0x7ffff6a01af0 "a:5", options=options@entry=0, 
    opened_path=opened_path@entry=0x0, context=context@entry=0x0) at /work/GIT/pecl-and-ext/xz-codemasher/xz_fopen_wrapper.c:440
#10 0x00007ffff7faf4f3 in zif_xzopen (execute_data=<optimized out>, return_value=0x7ffff6a15070) at /work/GIT/pecl-and-ext/xz-codemasher/xz.c:111
#11 0x00005555558992f6 in ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER () at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/Zend/zend_vm_execute.h:1393
#12 execute_ex (ex=0x12c494) at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/Zend/zend_vm_execute.h:110775
#13 0x00005555558947ae in zend_execute (op_array=0x7ffff6a94400, return_value=<optimized out>) at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/Zend/zend_vm_execute.h:115989
#14 0x0000555555908dc6 in zend_execute_script (type=type@entry=8, retval=0x7ffff6a15020, retval@entry=0x0, file_handle=file_handle@entry=0x7fffffffb960)
    at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/Zend/zend.c:1977
#15 0x000055555577ffb8 in php_execute_script_ex (primary_file=<optimized out>, retval=retval@entry=0x0) at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/main/main.c:2589
#16 0x000055555578026b in php_execute_script (primary_file=<optimized out>) at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/main/main.c:2629
#17 0x000055555590b0bf in do_cli (argc=argc@entry=94, argv=argv@entry=0x555555e283c0) at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/sapi/cli/php_cli.c:933
#18 0x000055555590b86a in do_php_cli (argc=94, argv=0x555555e283c0) at /usr/src/debug/php86-php-8.6.0~beta3-1.fc43.remi.x86_64/sapi/cli/php_cli.c:1346
#19 0x00007ffff6c115b5 in __libc_start_call_main () from /lib64/libc.so.6
#20 0x00007ffff6c11668 in __libc_start_main_impl () from /lib64/libc.so.6
#21 0x000055555545e965 in _start ()

• self is freed in php_xziop_close
• buffers are allocated only if php_xz_init_encoder/php_xz_init_decoder is called