Fix segmentation fault in nr-ru

executables/nr-ru.c

@@ -746,9 +746,9 @@ void tx_rf(RU_t *ru,int frame,int slot, uint64_t timestamp) {
       // currently we switch beams every 10 slots (should = 1 TDD period in FR2) and we take the beam index of the first symbol of the first slot of this period
       int beam=0;
       if (slot%10==0) {
-	if (ru->common.beam_id[0][slot*fp->symbols_per_slot] < 8) {
-	  beam = ru->common.beam_id[0][slot*fp->symbols_per_slot] | 8;
-	}
+        if ( ru->common.beam_id && (ru->common.beam_id[0][slot*fp->symbols_per_slot] < 8)) {
+          beam = ru->common.beam_id[0][slot*fp->symbols_per_slot] | 8;
+        }
       }
       /*
       if (slot==0 || slot==40) beam=0|8;