Apache2 Warning

hello,
i’m disable apache2.service (sudo systemctl disable apache2.service but i see:
Synchronizing state of apache2.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install disable apache2
Use of uninitialized value $service in hash element at /usr/sbin/update-rc.d line 26, line 45.
insserv: warning: current start runlevel(s) (empty) of script apache2' overrides LSB defaults (2 3 4 5). insserv: warning: current stop runlevel(s) (0 1 2 3 4 5 6) of script apache2’ overrides LSB defaults (0 1 6).
Use of uninitialized value $service in hash element at /usr/sbin/update-rc.d line 26, line 45.
insserv: warning: current start runlevel(s) (empty) of script apache2' overrides LSB defaults (2 3 4 5). insserv: warning: current stop runlevel(s) (0 1 2 3 4 5 6) of script apache2’ overrides LSB defaults (0 1 6).
Does anyone have an idea about this alert?