Fixed seeking behavior of property track with discrete interpolation

(cherry picked from commit 6613d9cf67e75237dd4f234f32d73bf48aa9defd)

scene/animation/animation_tree.cpp

@@ -954,7 +954,7 @@ void AnimationTree::_process_graph(float p_delta) {
 
 							Variant::interpolate(t->value, value, blend, t->value);
 
-						} else if (delta != 0) {
+						} else {
 							List<int> indices;
 							a->value_track_get_key_indices(i, time, delta, &indices);