take_gold() crash with GOLDOBJ

Possible fix for B10001.
When the code went into case 3 in cursed_book(),
the game hung in an endless loop in take_gold().
The call stack was:
    take_gold() line 22 + 10 bytes
    cursed_book(int 2) line 124
    study_book(obj * 0x00968860) line 421 + 19 bytes
    doread() line 130 + 9 bytes
    rhack(char * 0x005b8eac in_line) line 1813 + 3 bytes
    moveloop() line 405 + 7 bytes
    main(int 3, char * * 0x00962ac0) line 93

src/sit.c

@@ -17,9 +17,10 @@ take_gold()
 		flags.botl = 1;
 	}
 #else
-        struct obj *otmp;
+        struct obj *otmp, *nobj;
 	int lost_money = 0;
-	for (otmp = invent; otmp; otmp = otmp->nobj) {
+	for (otmp = invent; otmp; otmp = nobj) {
+		nobj = otmp->nobj;
 		if (otmp->oclass == COIN_CLASS) {
 			lost_money = 1;
 			delobj(otmp);