segfault in 2.6 and master, while parsing template parameters in C++ code.

Something in the commits between a1e3a5d and 2198fa9 has introduced a segfault
in CPlusPlus::ClassOrNamespace::nestedType(CPlusPlus::name const*,
CPlusPlus::ClassOrNamespace*). It happens at line 735, "_alreadyConsideredTemplates.contains(templId)".

AMAOF this call goes in the AlreadyConsideredClassContainer::contains(), and reaches the line 65 in there (if (existingItem->isEqualTo(item))) before crashing (because existingItem is not accessible), but I guess the reason of the crash is the fact that templId is not fully constructed.

In my particular case, templId describes an std::map<int, XX>, where XX is a local (internal to my project) typedef, that doesn't seem to get referenced correctly inside the templId data structure (the templId->templateArguments[1]._type is marked as <not accessible> in the debugger).

This segfault is present in both 2.6 and master branch. I just discovered it
as it happens at startup, upon reloading one of my most used sessions, while
loading/parsing the current opened file (C++). If I remove the session
configuration, I can start QtCreator correctly and I can load other files, but when loading this particular one (a rather large so no point in attaching it here), I get the crash again. 100% reproducible.

I attach the backtraces as dumped by QtCreator, but I find them unuseable.

NOTE: I am sure about the range of commits I indicate at the beginning because it was version a1e3a5d that I used without problem up until today to edit the exact same file that now makes QtCreator crash.