COMP: Fix uninitialized variable warning in vtkIGTLToMRMLTrajectory.
COMP: Fix uninitialized variable warning in vtkIGTLToMRMLTrajectory.

This commit addresses the following warning:

/home/kitware/Dashboards/Nightly/Slicer-0-build/OpenIGTLinkIF/MRML/vtkIGTLToMRMLTrajectory.cxx: In member function 'int vtkIGTLToMRMLTrajectory::PrepareTrajectoryElement(igtl::SmartPointer<igtl::TrajectoryElement>&, vtkMRMLNode*)':
/home/kitware/Dashboards/Nightly/Slicer-0-build/OpenIGTLinkIF/MRML/vtkIGTLToMRMLTrajectory.cxx:396: warning: 'rgba' may be used uninitialized in this function [-Wuninitialized]
/home/kitware/Dashboards/Nightly/Slicer-0-build/OpenIGTLinkIF/MRML/vtkIGTLToMRMLTrajectory.cxx:397: warning: 'opacity' may be used uninitialized in this function [-Wuninitialized]

Fixes #41

IGSIO/OpenIGTLinkIO,IGSIO/OpenIGTLinkIO