column: fix leading space characters bug

The bug has been introduced during column(1) rewrite. The function
read_input() need to skip leading space only temporary to detect empty
lines, but the rest of the code has to use the original buffer (line).

Addresses: #575
Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1560283
Signed-off-by: Karel Zak <kzak@redhat.com>

text-utils/column.c

@@ -452,7 +452,7 @@ static int read_input(struct column_control *ctl, FILE *fp)
 		if (!str || !*str)
 			continue;
 
-		wcs = mbs_to_wcs(str);
+		wcs = mbs_to_wcs(buf);
 		if (!wcs)
 			err(EXIT_FAILURE, _("read failed"));