Description:
------------
I believe the bug is caused by using strlen with null, fgets (probably) returns NULL on empty files.

https://github.com/winlibs/wineditline/blob/master/src/history.c#L270

    eof = fgets(&line[s], _EL_BUF_LEN, file);
    line_len = (int)strlen(line);



Test script:
---------------
<?php
touch("empty.file");
readline_read_history("empty.file");


Expected result:
----------------
Nothing

Actual result:
--------------
(227c.1c20): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
php7!read_history+0xe3:
00007ff9`d89bb8c3 40383413        cmp     byte ptr [rbx+rdx],sil ds:00000223`0ea15000=??
0:000> k
Child-SP          RetAddr           Call Site
000000ac`d79fbc20 00007ff9`d884d87a php7!read_history+0xe3 [e:\repo\winlibs_wineditline\src\history.c @ 270]
000000ac`d79fbc70 00007ff9`d872b875 php7!zif_readline_read_history+0x5a [c:\php-snap-build\php71\vc14\x64\php-7.1.13\ext\readline\readline.c @ 420]
000000ac`d79fbca0 00007ff9`d8708aa0 php7!ZEND_DO_ICALL_SPEC_RETVAL_UNUSED_HANDLER+0x55 [c:\php-snap-build\php71\vc14\x64\php-7.1.13\zend\zend_vm_execute.h @ 638]
000000ac`d79fbce0 00007ff9`d8751c7d php7!execute_ex+0x80 [c:\php-snap-build\php71\vc14\x64\php-7.1.13\zend\zend_vm_execute.h @ 432]
000000ac`d79fbd30 00007ff9`d87519d9 php7!zend_execute+0x14d [c:\php-snap-build\php71\vc14\x64\php-7.1.13\zend\zend_vm_execute.h @ 475]
000000ac`d79fbd60 00007ff9`d87517a7 php7!zend_execute_scripts+0xa9 [c:\php-snap-build\php71\vc14\x64\php-7.1.13\zend\zend.c @ 1483]
000000ac`d79fbde0 00007ff6`a06128e6 php7!php_execute_script+0x277 [c:\php-snap-build\php71\vc14\x64\php-7.1.13\main\main.c @ 2577]
000000ac`d79fe990 00007ff6`a061375e php!do_cli+0x996 [c:\php-snap-build\php71\vc14\x64\php-7.1.13\sapi\cli\php_cli.c @ 994]
000000ac`d79ff5b0 00007ff6`a061b5a9 php!main+0x67e [c:\php-snap-build\php71\vc14\x64\php-7.1.13\sapi\cli\php_cli.c @ 1381]
000000ac`d79ff7c0 00007ffa`10431fe4 php!__scrt_common_main_seh+0x11d [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl @ 253]
000000ac`d79ff800 00007ffa`124cefb1 KERNEL32!BaseThreadInitThunk+0x14
000000ac`d79ff830 00000000`00000000 ntdll!RtlUserThreadStart+0x21