This article describes how to disable the alert/log "IPV6 Packet dropped with unspecified source and IP" because you're not using IPv6
This is a generic log message which is related to IPv6
Even if you are not running your network on IPv6 these packets are still sent (because Windows has IPv6 enabled by default) and that is the reason SonicWall listens these packets .It drops them as they are irrelevant for SonicWall.
Please follow these steps to turn these messages off:
Login to the firewall GUI
Go to Log | Settings and expand the category Network
Expand the sub-category IP
Uncheck the Alert checkbox for the log "IPV6 Packet dropped with unspecified source and IP alerts"