Created attachment 226171 [details]
Testcase and patch

Given foo.h and a default generated Doxygen file where only HIDE_UNDOC_MEMBERS = YES and GENERATE_TREEVIEW = YES have changed.

/*!
  My X.
*/
class X
{
public:
  /// foo
  /// @{

  /// Nope.
  void what();
  /// @}

  void who();
};

The who() member function will be visible in the tree view although it hasn't been documented. The link from the treeview will lead to a non-existing anchor in the documentation of X.

Attached is a small patch to index.cpp to check for HIDE_UNDOC_MEMBERS and hasDocumentation before adding an entry to the treeview.