remove unnecessary null-check on gold_detect()

`sobj` here is always non-null, otherwise it leads segv at earlier code.

src/detect.c

@@ -367,7 +367,6 @@ gold_detect(struct obj *sobj)
     if (!gk.known) {
         /* no gold found on floor or monster's inventory.
            adjust message if you have gold in your inventory */
-        if (sobj) {
         char buf[BUFSZ];
 
         if (gy.youmonst.data == &mons[PM_GOLD_GOLEM])
@@ -386,7 +385,6 @@ gold_detect(struct obj *sobj)
             Strcpy(buf, "You feel materially poor.");
 
         strange_feeling(sobj, buf);
-        }
         return 1;
     }
     /* only under me - no separate display required */