XML : What is happening here? When I try to run this code, the following error appears

            -- Creating a procedure to convert DB to XML           CREATE OR REPLACE PROCEDURE XML_OUTPUT AS           BEGIN  -- Declaring a ref cursor and a variable of type XMLTYPE  DECLARE    refcursor SYS_REFCURSOR;    wxmltype XMLTYPE;  BEGIN  -- Prompting the user to input the range of database to be converted  dbms_output.put_line('Input the min value of MESSID');  -- Declaring the ref cursor and pointing it to a select variable    OPEN refcursor FOR SELECT messname,                              studentname                               FROM studentsmessdata                              -- Accepting user input for range                              WHERE messid > &messid;     wxmltype:= XMLTYPE(refcursor);    -- printing the database as XML    dbms_output.put_line(wxmltype.getClobVal);  END;    NULL;  END XML_OUTPUT;    

The following error appears:

Error: PLS-00801: internal error [ph2csql_strdef_to_diana:bind] Error(9,22): PL/SQL: SQL Statement ignored Error(12,34): PL/SQL: ORA-06544: PL/SQL: internal error, arguments:
[ph2csql_strdef_to_diana:bind], [], [], [], [], [], [], []