was attempting to max enchant a diamond sword. had a mending book that had blast protection 4 on it. my diamond sword had sharpness 5, looting 3, unbreaking 3, and sweeping edge 3. when i combined the book with the sword it added the blast protection 4 to the sword. i was in creative mode at the time it was done, though that shouldn't matter

What I expected to happen was...:
i assumed it would have not added the blast protection as it is not an enchantment that is compatible with swords.

What actually happened was...:
the sword was enchanted with blast protection 4

Steps to Reproduce:
1. I was enchanting a diamond sword in survival. combined the sword with a sharpness 4 looting 2 book
2. separately combined a sharpness 3 book with another sharpness 3 to make another sharpness 4 book, then combined that book with another looting 2 book to make the sword sharpness 5 looting 3.
3. combined an unbreaking 3 book with sweeping edge 3. and at this point i had run out of levels so i switched to creative mode and combined the sword with this new book.

4. i had obtained a mending, blast protection 4 book from fishing and decided to use it on my sword. at this time, the sword was sharpness 5, looting 3, unbreaking 3 and sweeping edge 3. but when i added this new book, it added mending as I had wanted, but also added the blast protection.