Revert "Revert "Always log the type coming out of an nqp::decont""

This reverts commit 9481289.

The original commit is clearly innocent. It just unlocked more optimizations
which uncovered quite a few spesh bugs. But hiding those won't get them fixed,
so let's see what bugs come our way.

src/core/interp.c

@@ -3101,12 +3101,12 @@ void MVM_interp_run(MVMThreadContext *tc, void (*initial_invoke)(MVMThreadContex
                 cur_op += 4;
                 if (obj && IS_CONCRETE(obj) && STABLE(obj)->container_spec) {
                     STABLE(obj)->container_spec->fetch(tc, obj, r);
-                    if (MVM_spesh_log_is_logging(tc))
-                        MVM_spesh_log_decont(tc, prev_op, r->o);
                 }
                 else {
                     r->o = obj;
                 }
+                if (MVM_spesh_log_is_logging(tc))
+                    MVM_spesh_log_decont(tc, prev_op, r->o);
                 goto NEXT;
             }
             OP(setcontspec): {