Process: com.tarang.grocery, PID: 7824 java.lang.NullPointerException: Can't pass null for argument 'pathString' in child()

Question

private void loadShopInfo(ModelOrderUser modelOrderUser, final HolderOrderUser holder) { DatabaseReference ref = FirebaseDatabase.getInstance().getReference("Users"); ref.child(modelOrderUser.getOrderTo()) .addValueEventListener (new ValueEventListener() { @Override public void onDataChange (@NonNull DataSnapshot dataSnapshot) { String shopName = ""+dataSnapshot.child("shopName").getValue(); holder.shopNameTv.setText(shopName); }

                @Override
                public void onCancelled(@NonNull DatabaseError error) {

                }
            } );
}