Fix: dipping into restore ability with no effect resulted in insane obj

The code always returned early, rather than only returning early when
the potion got used up. In cases where the potion didn't do anything,
this resulted in in_use still being set (and no "Interesting..." message
being produced), causing sanity check failures.

Author: copperwater

src/potion.c

@@ -3122,9 +3122,10 @@ potion_dip(struct obj *obj, struct obj *potion)
         }
         if (learn_it && potion->dknown)
             makeknown(POT_RESTORE_ABILITY);
-        if (did_something)
+        if (did_something) {
             poof(potion); /* includes trycall if dknown */
-        return ECMD_TIME;
+            return ECMD_TIME;
+        }
     }
  more_dips: