check if pdef_ is not a null ptr in TRRT. closes #117
check if pdef_ is not a null ptr in TRRT. closes #117

jvgomez/ompl,jvgomez/ompl,florianhauer/ompl,utiasASRL/batch-informed-trees,sonny-tarbouriech/ompl,sonny-tarbouriech/ompl,utiasASRL/batch-informed-trees,florianhauer/ompl,utiasASRL/batch-informed-trees,jvgomez/ompl,davetcoleman/ompl,jvgomez/ompl,davetcoleman/ompl,florianhauer/ompl,jvgomez/ompl,jvgomez/ompl,florianhauer/ompl,sonny-tarbouriech/ompl,florianhauer/ompl,davetcoleman/ompl,davetcoleman/ompl,davetcoleman/ompl,utiasASRL/batch-informed-trees,davetcoleman/ompl,utiasASRL/batch-informed-trees,sonny-tarbouriech/ompl,florianhauer/ompl,sonny-tarbouriech/ompl,utiasASRL/batch-informed-trees,sonny-tarbouriech/ompl