The BGradient class is a bit strange as it can store any gradient on its
own, butonly the subclasses allow to set some of the fields.
In the asignment operator, the non-base data (which is in an union) was
not copied over.
More importantly, the missing copy constructor led to the default
implementation being used, and BList (used for the color stops) was
being copied using its default copy constructor, resulting in the two
BGradient (original and copy) poinitng to the same stops data. Heap
corruption resulted whenever one of them was deleted.
Having a working copy ocnstructor fixes this. The alternative is making
the copy constructor private or protected to make sure gradients are not
copied, since normally you'd copy only the subclasses, preserving the
C++ type. However there is nothing enforcing that, and manipulating a
BGradient copied from a subclass works just fine.
Change-Id: I28e733eb8a2970b76ae623eabb75ef8435f508af
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3144
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
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