Fix null handling in removeAbove/BelowValue
Fix null handling in removeAbove/BelowValue

alexanderzobnin/grafana-zabbix,alexanderzobnin/grafana-zabbix,alexanderzobnin/grafana-zabbix,alexanderzobnin/grafana-zabbix,alexanderzobnin/grafana-zabbix,alexanderzobnin/grafana-zabbix