[Fix] Some more fixes for low contrast fonts detector
[Fix] Some more fixes for low contrast fonts detector

minaevmike/rspamd,minaevmike/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,minaevmike/rspamd,minaevmike/rspamd,minaevmike/rspamd,AlexeySa/rspamd,minaevmike/rspamd,minaevmike/rspamd,AlexeySa/rspamd,minaevmike/rspamd,AlexeySa/rspamd,minaevmike/rspamd