ifnull isn't really required when doing `!= 'anything'` because if it's null then value will be falsy.
ifnull is only required when checking `= ''` if you treat `null = ''`
Actuall better fix would be make things explcitly non-nullable, then we won't ever have to add this on such fields.
ref: https://github.com/frappe/frappe/pull/21822