My bug was in this line of code:

formContext.getControl("wdps_base_salesorderdetail")).addCustomView(viewId, "product", "Basisprodukt", fetchXml, gridLayout, true);

I passed the wrong logicalName (second parameter). It shoud be "salesorderdetail" rather than "product". The strange thing is the behaviour of Dynamics CRM, because the error-message guides me to the wrong direction and I forgot to have a closer look at the code. The other strange thing was, that Dynamics CRM adds an fix parameter to the fetchxml, this is the main-attribute of the entity passed as second parameter. In my case attribute 'name' was the attribute of product.

thx for reading :)