Fix give not to wipe out concurrect updates

give() reads the sector, prompts for input, updates the sector and
writes it back, triggering a generation oops.  Any updates made by
other threads during the yield are wiped out, triggering a seqno
mismatch oops.

src/lib/commands/give.c

@@ -62,6 +62,7 @@ give(void)
 	    return RET_SYN;
 	if ((amt = atoi(p)) == 0)
 	    return RET_SYN;
+	check_sect_ok(&sect);
 	n = sect.sct_item[ip->i_uid];
 	if (amt < 0 && -amt > n) {
 	    m = 0;