uc-taxes uc_vat condition action problem

Hi, I'm from Germany, and there's the problem to have different vat levels: 19% and 7%. So I don't want to create different classes with different vat and attributes, instead I want to create different VAT levels and try to start with conditions and actions. To get this done, I tested like this:

Made this two taxes with label 19% and 7 %.
Then I made an attribute with options (radiobuttons) with 19 and 7 percent.
I added this attribute to a class I made called "category1". By default 19% is pre-selected.
The condition I chosed is as follows: If 19% is chosen, the 19% tax is activated. Success: The shopping Cart shows this 19%. If the condition 7% is chosen the tax 7% is activated.

BUT: Instead of getting the column and the subtitle shown with the correct amount, I don't see anything but the label of the correct attributes.

Instead the whole time, when I create an article, I get the following message:

"warning: Invalid argument supplied for foreach() in /var/www/ubercart-6/sites/all/modules/ubercart/uc_attribute/uc_attribute.ca.inc on line 38"

The code of line 38 is:

 $match = unserialize($settings['attribute_option']);

  foreach ($order->products as $product) {
    if (!isset($product->data['attributes'])) {
      continue;
    }...

So what's the problem or what did I misunderstood?

The attachement has two Images: first with action and without the amount of taxes, second without action and therefor with the double amount of taxes ( the difference from 19% and 7% of taxes). I want to use the attribute/option as a trigger, so what's my problem???

Thx in advance,

maen

PS: What I forgot: I also use the uc_vat Module.