Fix piechart clean slice.
Fix piechart clean slice.

Issue: #380

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