BUG: Fix memory leak in TubeToTubeGraph
BUG: Fix memory leak in TubeToTubeGraph

Change-Id: I598834e45d5d56bb7d759958b1e9aecd2213b091

matthieuheitz/TubeTK,matthieuheitz/TubeTK,aylward/ITKTubeTK,KitwareMedical/TubeTK,LucasGandel/TubeTK,KitwareMedical/ITKTubeTK,cdeepakroy/TubeTK,LucasGandel/TubeTK,sumedhasingla/TubeTK,sumedhasingla/TubeTK,thewtex/TubeTK,KitwareMedical/TubeTK,KitwareMedical/TubeTK,LucasGandel/TubeTK,aylward/ITKTubeTK,matthieuheitz/TubeTK,KitwareMedical/ITKTubeTK,KitwareMedical/ITKTubeTK,sumedhasingla/TubeTK,aylward/ITKTubeTK,thewtex/TubeTK,matthieuheitz/TubeTK,thewtex/TubeTK,cdeepakroy/TubeTK,KitwareMedical/TubeTK,sumedhasingla/TubeTK,LucasGandel/TubeTK,thewtex/TubeTK,cdeepakroy/TubeTK,KitwareMedical/ITKTubeTK,aylward/ITKTubeTK,cdeepakroy/TubeTK