Hopefully fixed for the next release. For that scene, the user should now be able to select a penis (if applicable) before moving on to the scene.
From what I can assume, this bug is mainly due to an index error where the coder forgot to define a specific penis index, so the game will try to use the "default" value. The issue is, you might have done a scene where you could choose a penis or strapon, and after choosing strapon, the default index will shift to a non-penis index. So when a penis-only scene happens and the default value isn't reset, it will use that same default index and because the text is only parsing for something in the penis array, the index is out of range and the game spits out an error.