fix add_one_tobill() 'fixme'

Not exhaustively tested.

src/mkobj.c

@@ -722,12 +722,12 @@ bill_dummy_object(struct obj *otmp)
     dummy->timed = 0;
     copy_oextra(dummy, otmp);
     if (has_omid(dummy))
-        free_omid(dummy); /* only one association with m_id*/
+        free_omid(dummy); /* only one association with m_id */
     if (Is_candle(dummy))
         dummy->lamplit = 0;
     dummy->owornmask = 0L; /* dummy object is not worn */
     addtobill(dummy, FALSE, TRUE, TRUE);
-    if (cost)
+    if (cost && dummy->where != OBJ_DELETED)
         alter_cost(dummy, -cost);
     /* no_charge is only valid for some locations */
     otmp->no_charge = (otmp->where == OBJ_FLOOR

src/shk.c

@@ -3213,35 +3213,43 @@ unpaid_cost(
     return amt;
 }
 
+/* add 'obj' to 'shkp's bill */
 staticfn void
-add_one_tobill(struct obj *obj, boolean dummy, struct monst *shkp)
+add_one_tobill(
+    struct obj *obj,
+    boolean dummy, /* True: obj is used up so goes on bill differently */
+    struct monst *shkp)
 {
     struct eshk *eshkp;
     struct bill_x *bp;
     int bct;
+    boolean unbilled = FALSE;
 
-    if (!billable(&shkp, obj, *u.ushops, TRUE))
-        return;
     eshkp = ESHK(shkp);
-
-    if (eshkp->billct == BILLSZ) {
-        You("got that for free!");
-        /*
-         * FIXME:
-         *  What happens when this is a dummy object?  It won't be on any
-         *  object list.
-         */
-        return;
-    }
-
     /* normally bill_p gets set up whenever you enter the shop, but obj
        might be going onto the bill because hero just snagged it with
        a grappling hook from outside without ever having been inside */
     if (!eshkp->bill_p)
-        eshkp->bill_p = &(eshkp->bill[0]);
+        eshkp->bill_p = &eshkp->bill[0];
+
+    if (!billable(&shkp, obj, *u.ushops, TRUE)) {
+        /* shk doesn't want it */
+        unbilled = TRUE;
+    } else if (eshkp->billct == BILLSZ) {
+        /* shk's bill is completely full */
+        You("got that for free!");
+        unbilled = TRUE;
+    }
+    /* if not on any list (probably from bill_dummy_object() which creates
+       a new OBJ_FREE object), don't leave unmanaged object hanging around */
+    if (unbilled) {
+        if (obj->where == OBJ_FREE)
+            dealloc_obj(obj); /* change to obj->where==OBJ_DELETED */
+        return;
+    }
 
     bct = eshkp->billct;
-    bp = &(eshkp->bill_p[bct]);
+    bp = &eshkp->bill_p[bct];
     bp->bo_id = obj->o_id;
     bp->bquan = obj->quan;
     if (dummy) {              /* a dummy object must be inserted into  */