net/mlx5: Fix NULL pointer dereference in extended destination

The cited commit refactored the encap id into a struct pointed from the
destination.
Bug fix for the case there is no encap for one of the destinations.

Fixes: 2b688ea5 ("net/mlx5: Add flow steering actions to fs_cmd shim layer")
Signed-off-by: NEli Britstein <elibr@mellanox.com>
Reviewed-by: NRoi Dayan <roid@mellanox.com>
Signed-off-by: NSaeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/fs_cmd.c

@@ -507,7 +507,8 @@ static int mlx5_cmd_set_fte(struct mlx5_core_dev *dev,
 				MLX5_SET(dest_format_struct, in_dests,
 					 destination_eswitch_owner_vhca_id,
 					 dst->dest_attr.vport.vhca_id);
-				if (extended_dest) {
+				if (extended_dest &&
+				    dst->dest_attr.vport.pkt_reformat) {
 					MLX5_SET(dest_format_struct, in_dests,
 						 packet_reformat,
 						 !!(dst->dest_attr.vport.flags &