you do not have to delete library in main window select *.dsn file than right click >> edit object propertiee
now in this window in Comp Ref column check the part which does not have any footprint assigned to it and than give it some ref des
Actually you have to add refdes for that footprint.
open the footprint(.dra).
go to layout-labels-refdes and assign refdes in the class and sub class you need it.
please have a look of the attachment.
after that save the symbol(.dra) and try.