Depending of the size of your long datatype, there often is really not possible to solve this problem, it is very clear. It is not a large backdraw, in fact. Oracle accepted this.
Do you have a real problem, like a performance one, based only on this issue, or the problem is the chained rows themselves? If they are not really bothering you, let them alone!
In case you really need to repair this, try export the table data, re-create the table with some storage parameters that fit your needs, then load the data.
If is not possible to drop and re-create the table, then is nothing to do.
My oppinion. Bye!