added an obidebug() line

src/obidmscolumn.c

@@ -1010,6 +1010,7 @@ int obi_truncate_column_to_lines_used(OBIDMS_column_p column)
 	if (column_file_descriptor < 0)
 	{
 		obi_set_errno(OBICOL_UNKNOWN_ERROR);
+		obidebug(1, "\nError getting the file descriptor of a column file");
 		free(column_file_name);
 		return -1;
 	}