Update spare.cpp

Uninitialized variable size is O'K?

spare.cpp
/Symbian/Projects/SDL/scummvm/common/serializer.h: In member function 'void CGE2::Spare::sync(Common::Serializer&)':
/Symbian/Projects/SDL/scummvm/common/serializer.h: 100: warning: 'size' may be used uninitialized in this function
/Symbian/Projects/SDL/scummvm/engines/cge2/spare.cpp:45: note: 'size' was declared here