ora 1561 when dropping tablespace

Drop tablespace users including contents;

give me ora-1561 error.

This tablespace has no objects.

select

total.file_name fname,

total.bytes/1024 totsiz,

nvl(sum(free.bytes)/1024,0) avasiz,

(1-nvl(sum(free.bytes),0)/total.bytes)*100 pctusd

total.file_name fname, total.bytes/1024 totsiz, nvl(sum(free.bytes)/1024,0) avasiz, (1-nvl(sum(free.bytes),0)/total.bytes)*100 pctusd

.file_name fname, total.bytes/1024 totsiz, nvl(sum(free.bytes)/1024,0) avasiz, (1-nvl(sum(free.bytes),0)/total.bytes)*100 pctusd

.bytes/1024 totsiz, nvl(sum(free.bytes)/1024,0) avasiz, (1-nvl(sum(free.bytes),0)/total.bytes)*100 pctusd

nvl(sum(free.bytes)/1024,0) avasiz, (1-nvl(sum(free.bytes),0)/total.bytes)*100 pctusd (1-nvl(sum(free