feat: filter out nil actions in action waiter (#464) (#471)

Filter out nil actions, to help users of the function.

Backport commit 4fc9a40 into
release-1.x

hcloud/action_waiter.go

@@ -21,6 +21,9 @@ var _ ActionWaiter = (*ActionClient)(nil)
 //
 // The handleUpdate callback is called every time an action is updated.
 func (c *ActionClient) WaitForFunc(ctx context.Context, handleUpdate func(update *Action) error, actions ...*Action) error {
+	// Filter out nil actions
+	actions = slices.DeleteFunc(actions, func(a *Action) bool { return a == nil })
+
 	running := make(map[int]struct{}, len(actions))
 	for _, action := range actions {
 		if action.Status == ActionStatusRunning {