ORA-00604, ORA-01405 when dropping a table

# problem - errors when trying to drop a table

SQL> drop table test;
drop table test
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-01405: fetched column value is NULL

# cause - select into from dual failed because dummy was null

# fix

update dual set dummy = 'X';