Power Query- Code Cheater Code for IF equals and Does Not Equal Null

I wanted my script to look at values but ignore the "Null" values for the comparison 

Table.AddColumn(#"Split column by delimiter 1", "PSStudentAddressMatches", each if [PSMailingAddress.1] <> [PSMailingAddress.2] and [PSMailingAddress.2] <> null  then "PS Address Flag"

else if [PSMailingAddress.1] <> [PSMailingAddress.3] and [PSMailingAddress.3] <> null  then "PS Address Flag"

else if [PSMailingAddress.1] <> [PSMailingAddress.4] and [PSMailingAddress.4] <> null then "PS Address Flag"

else if [PSMailingAddress.1] <> [PSMailingAddress.5] and [PSMailingAddress.5] <> null then "PS Address Flag"

else if [PSMailingAddress.1] <> [PSMailingAddress.6] and [PSMailingAddress.6] <> null then "PS Address Flag"

else if [PSMailingAddress.1] <> [PSMailingAddress.7] and [PSMailingAddress.7] <> null  then "PS Address Flag"

else if [PSMailingAddress.1] <> [PSMailingAddress.8] and [PSMailingAddress.8] <> null then "PS Address Flag"  

else "OK")