Thanks for reporting - I can reproduce this. It's a problem with error handling.

(lldb) bt

• thread 0000026: tid = 0x2da4f35, 0x00007fff9421b866 libsystem_kernel.dylib__pthread_kill + 10, stop reason = signal SIGABRT frame #0: 0x00007fff9421b866 libsystem_kernel.dylib__pthread_kill + 10
  frame 0000001: 0x00007fff935c235c libsystem_pthread.dylibpthread_kill + 92 frame 0000002: 0x00007fff964c3b1a libsystem_c.dylibabort + 125
  frame 0000003: 0x00007fff8c6b2bee libsystem_malloc.dylibnanozone_error + 486 frame 0000004: 0x00007fff8c6b2db0 libsystem_malloc.dylib_nano_malloc_check_clear + 445
  frame 0000005: 0x00007fff8c6b16b0 libsystem_malloc.dylibnano_malloc + 35 frame 0000006: 0x00007fff8c6af868 libsystem_malloc.dylibmalloc_zone_malloc + 71
  frame 0000007: 0x00007fff8c6b027c libsystem_malloc.dylibmalloc + 42 frame 0000008: 0x0000000113d20392 QtCoreQString::QString(QChar const, int) + 66
  frame 0000009: 0x0000000113cfc438 QtCorequlltoa(unsigned long long, int, QChar) + 152 frame 0000010: 0x0000000113cf0734 QtCoreQLocalePrivate::unsLongLongToString(QChar, QChar, QChar, unsigned long long, int, int, int, unsigned int) + 68
  frame 0000011: 0x0000000113cf0a7b QtCoreQLocalePrivate::unsLongLongToString(unsigned long long, int, int, int, unsigned int) const + 59 frame 0000012: 0x0000000113d78775 QtCoreQTextStreamPrivate::putNumber(unsigned long long, bool) + 517
  frame 0000013: 0x0000000113d78911 QtCore`QTextStream::operator<<(void const) + 81
  frame 0000014: 0x0000000104452246 libCTKCore.0.1.dylibctk::qtHandleToString(handle=0x000000016345f000) + 86 at ctkUtils.cpp:392 frame 0000015: 0x0000000103f9f545 libCTKVisualizationVTKCore.0.1.dylib(anonymous namespace)::ctkVTKOutputWindow::DisplayErrorText(this=0x00006280000948c0, text=0x00006400001dd5b0) + 181 at ctkVTKErrorLogMessageHandler.cpp:95
  frame 0000016: 0x000000011689502c libvtkCommon.5.10.dylib`vtkOutputWindowDisplayErrorText(message=0x00006400001dd5b0) + 44 at vtkOutputWindow.cxx:41
  • frame 0000017: 0x0000000115123897 libvtkImaging.5.10.dylibvtkImageLogic::ThreadedRequestData(this=0x0000628000319350, (null)=0x0000608000a62680, (null)=0x0000628000211fb0, (null)=0x0000628000e6ee00, inData=0x0000620000015950, outData=0x0000620000015670, outExt=0x000000016345ee90, id=7) + 5287 at vtkImageLogic.cxx:274 frame 0000018: 0x00000001163960db libvtkFiltering.5.10.dylibvtkThreadedImageAlgorithmThreadedExecute(arg=0x0000000119a85b18) + 763 at vtkThreadedImageAlgorithm.cxx:199
    frame 0000019: 0x00007fff935c1899 libsystem_pthread.dylib_pthread_body + 138 frame 0000020: 0x00007fff935c172a libsystem_pthread.dylib_pthread_start + 137
    (lldb)

vtkOutputWindowDisplayErrorText is being called from inside a thread.

Here are the last few messages that are printed before the crash:

ERROR: In /Users/pieper/slicer4/latest/Slicer-superbuild/VTKv5/Imaging/vtkImageLogic.cxx, line 277
vtkImageLogic (0x628000319350): Execute: input1 NumberOfScalarComponents, 9, must match out input2 NumberOfScalarComponents 1

ERROR: In /Users/pieper/slicer4/latest/Slicer-superbuild/VTKv5/Imaging/vtkImageLogic.cxx, line 277
vtkImageLogic (0x628000319350): Execute: input1 NumberOfScalarComponents, 9, must match out input2 NumberOfScalarComponents 1

Execute: input1 NumberOfScalarComponents, 9, must match out input2 NumberOfScalarComponents 1

Note that as a workaround you can do the inverse registration (make MRHead the moving volume).

Problem was in the CloneVolume method not handling non-scalar volumes. Fixed in r23590.