-Werror,-Wuninitialized

(in CachedPrimitiveBase ctor: base class 'comphelper::OBaseMutex' is
uninitialized when used here to access 'comphelper::OBaseMutex::m_aMutex')

Change-Id: I30855a80ad9dbc3fa90e45d51d2a02794033f2f1