Morph relations + and -

[bulletproof-coding]

Hi. I saw this bug and it is not the first one #54401

Why do people mess with their lives and use these kind of relations anyway? They are slower than normal relations. I never used them and hope that I will never do.

I think that getting apples and oranges in 2 separate relations is better than getting fruits as a morph able relation.

Just because this is possible does not mean it should be used.