Crash due to assert commentPool.CurrentAllocs() == _commentPool.Untracked()

[smuellerDD]

When using Encfs (https://github.com/vgough/encfs), the patch https://github.com/leethomason/tinyxml2/commit/eb3ab0df5d184b84eb283c0806f6abee71e3409b causes the following assert:

../tinyxml2.cpp:2260: void tinyxml2::XMLDocument::Clear(): Zusicherung »_commentPool.CurrentAllocs() == _commentPool.Untracked()« nicht erfüllt.

I.e. the assert in tinyxml2::XMLDocument::Clear() is not fulfilled. When I use tinyxml with the code one git commit earlier, it works without the issue.