I'm currently referencing this field, Service_Order__r.Unit_Allocation_Value_Formula__c, in a template, but when the field is blank it is returning "#Error!" How can I return a blank value instead? Thanks!

Try this = 

IF(
    OR(
        AND(
            Package_Product__c = "Yes",
            NOT(ISBLANK(Opportunity.SBQQ__PrimaryQuote__c))
        ),
        BLANKVALUE(Opportunity.BESP_Grand_Total__c, 0) = 0
    ),
    NULL,
    ROUND(Opportunity.Amount * (ASP_Total__c / Opportunity.BESP_Grand_Total__c), 2)
)