Thanks and sorry, i didn't look into the resolved-part of the forum. I will remember that for the next time.

I can't empty the cursor by pressing Q while i'm holding a ghostitem. You have to "overwrite" it with an item in the inventory.
Example: you place a furnance and you don't have another one in the inventory. When point the cursor on the furnance and press Q to pick it up you get the ghostfurnance ...