php8.0: Compatibility fixes

app/admin/devices/edit-result.php

app/admin/devices/edit-snmp-result.php

app/admin/import-export/import-devices-check.php

app/admin/nameservers/edit-result.php

app/admin/ripe-import/import-subnets.php

app/admin/subnets/edit-vlan-dropdown.php

app/admin/subnets/edit.php

app/admin/version-check/index.php

app/admin/vlans/edit-domain-result.php

app/admin/vrf/edit-result.php

app/sections/menu/menu-tools-admin.php

app/subnets/addresses/address-modify-submit.php

app/subnets/scan/subnet-scan.php

app/subnets/subnet-details/subnet-details.php

app/tools/locations/single-location-map.php

app/tools/vlan/domains.php

functions/classes/class.Common.php

functions/classes/class.Tools.php

functions/classes/class.User.php