Qt crashes in Qt5Core|d.dll when QString::toUnicode(..) is called.

This bug possibly affects the Qt build process since during my Build I got 4 crashes (in minor components like using lrelease for Assitant language files, so Qt nearly finished to build), which were all located in Qt5Core|d.dll

The dissassembly shows:
827: return convertToUnicode(a.constData(), a.length(), 0);
5BD268E0 push 0
5BD268E2 mov ecx,dword ptr [a]
5BD268E5 call QByteArray::length (5B9AEAF2h)
5BD268EA push eax
5BD268EB mov ecx,dword ptr [a]
5BD268EE call QByteArray::constData (5B9A7A6Dh)
5BD268F3 push eax
5BD268F4 mov eax,dword ptr [ebp+8]
5BD268F7 push eax
5BD268F8 mov ecx,dword ptr [this]
5BD268FB mov edx,dword ptr [ecx] <-- Crash