Not sure about the error, but this task may work better using xp_Dirtree. Here is an example:
DROP TABLE IF EXISTS #Results
CREATE TABLE #Results
(
Subdirectory VARCHAR(300)
, depth INT
, [File] BIT
);
INSERT #Results
(
Subdirectory
, depth
, [File]
)
EXEC sys.xp_dirtree 'c:\temp', 0, 1;
SELECT * FROM #Results r WHERE [File] = 1