Handle NULL return of pullTpool()

executables/main-fs6.c

executables/nr-gnb.c

executables/nr-ru.c

executables/nr-ue.c

openair1/PHY/NR_TRANSPORT/nr_dlsch_coding.c

openair1/PHY/NR_UE_TRANSPORT/nr_dlsch_decoding.c

openair1/SCHED/phy_procedures_lte_eNb.c

openair1/SCHED_NR/fapi_nr_l1.c

openair1/SCHED_NR/phy_procedures_nr_gNB.c