warc: Simplify __archive_read_ahead check

A short read would lead to a NULL return value, thus the second check
will never be true.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>

libarchive/archive_read_support_format_warc.c

@@ -192,12 +192,9 @@ _warc_bid(struct archive_read *a, int best_bid)
 	(void)best_bid; /* UNUSED */
 
 	/* Check the first line, which should already be a record header. */
-	if ((hdr = __archive_read_ahead(a, 12U, &nrd)) == NULL) {
+	if ((hdr = __archive_read_ahead(a, 12, &nrd)) == NULL) {
 		/* Not enough data to identify this format. */
 		return -1;
-	} else if (nrd < 12) {
-		/* Not WARC; the magic string is at least 12 bytes. */
-		return -1;
 	}
 
 	/* Parse the record version number. */