How to check if cursor exists (open status)

You can use the CURSOR_STATUS function to determine its state.

IF CURSOR_STATUS('global','myCursor')>=-1
BEGIN
 DEALLOCATE myCursor
END

Close the cursor, if it is empty then deallocate it:

IF CURSOR_STATUS('global','myCursor') >= -1
 BEGIN
  IF CURSOR_STATUS('global','myCursor') > -1
   BEGIN
    CLOSE myCursor
   END
 DEALLOCATE myCursor
END