Resolve ROOT-9255 (Avoid RecursiveRemoving into already deleted collection).
Resolve ROOT-9255 (Avoid RecursiveRemoving into already deleted collection).

In some cases, fPrimitives has the kMustCleanup bit set which will lead
its destructor to call RecursiveRemove and since this pad is still
likely to be (indirectly) in the list of cleanups, we must set
fPrimitives to nullptr to avoid TPad::RecursiveRemove from calling
a member function of a partially destructed object.

olifre/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,karies/root,root-mirror/root,karies/root,olifre/root,root-mirror/root,olifre/root,karies/root,olifre/root,karies/root,olifre/root,karies/root,karies/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,karies/root,karies/root,karies/root,olifre/root,root-mirror/root,olifre/root