Description of Bug: Likely related to my inability to scribe books. After being unable to scribe books again tonight, I realized all eleven cups of ink I own have been used. (I have been pretty careful to only use one because I want to use the rest to write books, and I don't think the person who sold them to me used more than one cup before selling me the ink, though I didn't check individually at the time because it's kind of annoying to do so. Unfortunately, I've mixed up a lot of the cups of ink looking for a full one, so I can't say for certain which cups I actually used). I can pour a used cup of ink into an inkwell, but cannot pour a second used cup of ink into the same inkwell, because it already contains something. Likewise, if I pour a used cup of ink into an empty barrel, then attempt to pour a second used cup of ink into the barrel, I receive a notification that the barrel already contains something (I was hoping to put multiple partial cups of ink into a barrel and then be able to get a full cup out of it somehow). I can get the used cup of ink out if I use an empty cup on the barrel
Reproduction Steps:

1.  Have some amount of ink in a cup
2.  Pour into a larger container, such as a barrel or an inkwell
3.  Have some amount of ink in a second cup
4. Drag the second cup onto the same container

Error message (if applicable):
Screenshots:

Fixed.