incorrect condition for check result produce crash

[marakew]

if we have error for load dll at here https://github.com/wbenny/pdbex/blob/master/Source/PDB.cpp#L77 we are skip this condition https://github.com/wbenny/pdbex/blob/master/Source/PDB.cpp#L115 FAILED check for < 0 then we return FALSE so we crash when continue to deref pointer m_DataSource here https://github.com/wbenny/pdbex/blob/master/Source/PDB.cpp#L152