BUG: prevent crash when TransformFileReader transform list is empty

[ihnorton]

Fixes segfault reported here: https://discourse.slicer.org/t/loading-mat-matrix/2226
while reading MATLAB .mat file (into Slicer, but replicated independently) because ioTransformList is empty.

frame #0: 0x00000001148d4209 libITKIOTransformBase-4.13d.1.dylib`itk::TransformFileReaderTemplate<double>::Update(this=0x0000000146741000) at itkTransformFileReader.hxx:149
   146 	  // need to be initialized using the transform parameters.
   147 	  // kernelTransform->ComputeWMatrix() has to be called after the transform is read but
   148 	  // before the transform is used.
-> 149 	  std::string transformTypeName = ioTransformList.front()->GetNameOfClass();
   150 	  const size_t len = strlen("KernelTransform");// Computed at compile time in most cases
   151 	  if (transformTypeName.size() >= len
   152 	      && !transformTypeName.compare(transformTypeName.size()-len , len, "KernelTransform"))

[ihnorton]

FWIW

100% tests passed, 0 tests failed out of 2360

I guess CI failed due to compiler warnings.

[thewtex]

@ihnorton Thanks for the patch. Could it please be submitted to Gerrit?

[ihnorton]

Alright... (I thought you were taking PRs based on some of the othere recent ones here)

[ihnorton]

http://review.source.kitware.com/#/c/23232/

[thewtex]

Thanks, @ihnorton!