apply fix for null reference exception when propertyChanged is assigned but previousValues is null, closes pull request #5303
apply fix for null reference exception when propertyChanged is assigned but previousValues is null, closes pull request #5303

volkanceylan/Serenity,volkanceylan/Serenity,volkanceylan/Serenity,volkanceylan/Serenity,volkanceylan/Serenity