Qt3D: QOpenGL - Buffer memory leak

QOpenGL Buffers might not get freed in the backend, after a new mesh functor was created.

I encoutered this problem while rendering a mesh and changing its color over and over again during runtime. I double checked my code and made use of QSharedPointers when possible. The memory still grows and the application chrashes. I already talked with lemire_p about this and he proposed that I should report this bug.