message: FIX: add exception for wrong file name in ProjectionsReader
  This patch fixes
diff: @@ -145,9 +145,13 @@ void ProjectionsReader<TOutputImage>
  static bool firstTime = true;
  if(firstTime)
  rtk::RegisterIOFactories();
  + firstTime = false;
  itk::ImageIOBase::Pointer imageIO = itk::ImageIOFactory::CreateImageIO( m_FileNames[0].c_str(), itk::ImageIOFactory::FileModeType::ReadMode );
  + if(imageIO == nullptr)
  + itkGenericExceptionMacro(<< "Cannot create ImageIOFactory for file " << m_FileNames[0].c_str());
  +
  if(m_ImageIO != imageIO)
  {
  imageIO->SetFileName( m_FileNames[0].c_str() );
  