Fix gather redundancy seg fault

prrt/proto/types/block.c

@@ -17,10 +17,14 @@ static void gather_redundancy_packets(const PrrtBlock *block_ptr, gf *const *fec
             continue;
         }
 
-        while(idx_p[m] != -1) {
+        while(idx_p[m] != -1 && m < n) {
             m++;
         }
 
+        if(m == n) {
+          break;
+        }
+
         PrrtPacket_copy_payload_to_buffer(fec[m], packet, PRRT_PACKET_REDUNDANCY_HEADER_SIZE);
         idx_p[m] = packet->index;
     }