[bug]: `AddInvoice`: clearer error message when `peer_pubkey` used and peer is offline

[ZZiigguurraatt]

I try to add an asset invoice with a specific peer that is offline

a2c1cf9c97ec:/$ litcli ln addinvoice --asset_amount 44444 --asset_id 03b01073bef443026d3703511d58463687ecd668b65169bba9deefafa7a11cfd --rfq_peer_pubkey 035da0a856a9531f47efcef053c985cf02352a06eb3275fd3a6ae2fe8a17ca0887
[litcli] error adding invoice: rpc error: code = Unknown desc = error finding asset channel to use: no asset channels found for AssetSpecifier(id=03b01073bef443026d3703511d58463687ecd668b65169bba9deefafa7a11cfd, group_pub_key=) and peer=035da0a856a9531f47efcef053c985cf02352a06eb3275fd3a6ae2fe8a17ca0887
a2c1cf9c97ec:/$ 

and you can see it says "no asset channels found", but this is very misleading because when I run lncli listchannels, you can see there is a channel, it is just inactive because the peer is offline:

        {
            "active": false,
            "remote_pubkey": "035da0a856a9531f47efcef053c985cf02352a06eb3275fd3a6ae2fe8a17ca0887",
            "channel_point": "beae32c09c67005b7edc175902e81b07afc5a6828093988848b316de63075870:0",
            "chan_id": "70580763de16b3488898938082a6c5af071be8025917dc7e5b00679cc032aebe",
            "scid": "672901116264448",
            "scid_str": "612x1x0",
            "capacity": "100000",
            "local_balance": "50000",
            "remote_balance": "46920",
            "commit_fee": "2420",
            "commit_weight": "958",
            "fee_per_kw": "2500",
            "unsettled_balance": "0",
            "total_satoshis_sent": "0",
            "total_satoshis_received": "0",
            "num_updates": "0",
            "pending_htlcs": [],
            "csv_delay": 144,
            "private": true,
            "initiator": false,
            "chan_status_flags": "ChanStatusDefault",
            "local_chan_reserve_sat": "1062",
            "remote_chan_reserve_sat": "1000",
            "static_remote_key": false,
            "commitment_type": "SIMPLE_TAPROOT_OVERLAY",
            "lifetime": "1099",
            "uptime": "967",
            "close_address": "",
            "push_amount_sat": "50000",
            "thaw_height": 0,
            "local_constraints": {
                "csv_delay": 144,
                "chan_reserve_sat": "1062",
                "dust_limit_sat": "354",
                "max_pending_amt_msat": "99000000",
                "min_htlc_msat": "1",
                "max_accepted_htlcs": 83
            },
            "remote_constraints": {
                "csv_delay": 144,
                "chan_reserve_sat": "1000",
                "dust_limit_sat": "354",
                "max_pending_amt_msat": "99000000",
                "min_htlc_msat": "1",
                "max_accepted_htlcs": 83
            },
            "alias_scids": [
                "17592186044416000003",
                "17753318155189551152",
                "17789984115439910954",
                "17772434811583609595",
                "17848012179223763124",
                "17674028143836061454",
                "17649570934288698346",
                "17857899905265065434"
            ],
            "zero_conf": false,
            "zero_conf_confirmed_scid": "0",
            "peer_alias": "035da0a856a9531f47ef",
            "peer_scid_alias": "17592186044416000000",
            "memo": "",
            "custom_channel_data": {
                "funding_assets": [
                    {
                        "version": 1,
                        "asset_genesis": {
                            "genesis_point": "4f60b00603caf2dc752ed82d821e15dd933d1f8af9ce307fac551f1101392193:1",
                            "name": "Asset1",
                            "meta_hash": "827c23a4b1a5f4f9a9a42e61aa7bf7bf7e7925b4723728b60ad1918d632e2b0a",
                            "asset_id": "03b01073bef443026d3703511d58463687ecd668b65169bba9deefafa7a11cfd"
                        },
                        "amount": 200000000,
                        "script_key": "0250aaeb166f4234650d84a2d8a130987aeaf6950206e0905401ee74ff3f8d18e6",
                        "decimal_display": 3
                    }
                ],
                "local_assets": [],
                "remote_assets": [
                    {
                        "asset_id": "03b01073bef443026d3703511d58463687ecd668b65169bba9deefafa7a11cfd",
                        "amount": 200000000
                    }
                ],
                "outgoing_htlcs": [],
                "incoming_htlcs": [],
                "capacity": 200000000,
                "group_key": "020f907aaaa211319ad857f9fbbe0babe40d2277521b1b98e54b0c961b54d99923",
                "local_balance": 0,
                "remote_balance": 200000000,
                "outgoing_htlc_balance": 0,
                "incoming_htlc_balance": 0
            }
        },

We need to make the error message clearer to indicate that there are actually channels, they are just offline, so no RFQ could be attempted with an offline peer.