Undefined offset: -1 (vendor/captcha-com/captcha/lib/botdetect/CaptchaIncludes.php)

[bsv-huypham]

I have an error of Japanese captcha code.
I cann't find the reason, sometime it's happen in recent days (i don't change anything):
Undefined offset: -1 {"exception":"[object] (ErrorException(code: 0): Undefined offset: -1 at .../vendor/captcha-com/captcha/lib/botdetect/CaptchaIncludes.php:2)

log_error.txt

Please help me to fix this issue, this is very important to me.
Thanks & Regards.