Revert "fix crash on NULL gi.invent"

This reverts commit 378648bd9c.

The problem was triggered by marking the 'objlist' argument in
merge_choice() prototype with __attribute__((nonnull)) when it
shouldn't have been, then a followup which relied on that.  The
'objlist' argument might be Null.  Instead of passing its address to
force it to be non-Null, remove the attribute.

src/uhitm.c

@@ -2717,7 +2717,7 @@ mhitm_ad_sgld(
 
         if (mongold) {
             obj_extract_self(mongold);
-            if (merge_choice(&gi.invent, mongold)
+            if (merge_choice(gi.invent, mongold)
                     || inv_cnt(FALSE) < invlet_basic) {
                 addinv(mongold);
                 Your("purse feels heavier.");