converttopsbt given a funded tx produces a psbt that can't be signed

Create raw transaction

```
elements-cli createrawtransaction [] "{\"Azpsjg2XXT7phritvPLAv4PZM4QnCkCWHKiuA6jTWvW9CC91qwsvGJUD9rBPHNES5JSc5Hurqmh59Lko\":0.00001256}" 0 false "{\"Azpsjg2XXT7phritvPLAv4PZM4QnCkCWHKiuA6jTWvW9CC91qwsvGJUD9rBPHNES5JSc5Hurqmh59Lko\":\"b2e15d0d7a0c94e4e2ce0fe6e8691b9e451377f6e46e8045a86f7c4b5d4f0f23\"}"
0200000000000101230f4f5d4b7c6fa845806ee4f67713459e1b69e8e60fcee2e4940c7a0d5de1b20100000000000004e80343b01fc92b09d95c7917c1f1c28233dd7a1186d776703e6e6dd26732e20b44
```

Fund it

```
elements-cli fundrawtransaction 0200000000000101230f4f5d4b7c6fa845806ee4f67713459e1b69e8e60fcee2e4940c7a0d5de1b20100000000000004e80343b01fc92b09d95c7917c1f1c28233dd7a1186d776703e6e6dd26732e20b44e117a914800c73cf1b0788708b928fbae80c13cbdede5f788700000000
{
"hex": "020000000001c739fe40824f84fe84b7dc86f43d9f9956c04d1461baddf1033f595dd1367bc60000000000fdffffff0201230f4f5d4b7c6fa845806ee4f67713459e1b69e8e60fcee2e4940c7a0d5de1b20100000000000004e80343b01fc92b09d95c7917c1f1c28233dd7a1186d776703e6e6dd26732e20b44e117a914800c73cf1b0788708b928fbae80c13cbdede5f788701230f4f5d4b7c6fa845806ee4f67713459e1b69e8e60fcee2e4940c7a0d5de1b2010000000000000b59000000000000",
"fee": 0.00002905,
"changepos": -1
}
```
Convert it to a psbt

```

elements-cli converttopsbt 020000000001c739fe40824f84fe84b7dc86f43d9f9956c04d1461baddf1033f595dd1367bc60000000000fdffffff0201230f4f5d4b7c6fa845806ee4f67713459e1b69e8e60fcee2e4940c7a0d5de1b20100000000000004e80343b01fc92b09d95c7917c1f1c28233dd7a1186d776703e6e6dd26732e20b44e117a914800c73cf1b0788708b928fbae80c13cbdede5f788701230f4f5d4b7c6fa845806ee4f67713459e1b69e8e60fcee2e4940c7a0d5de1b2010000000000000b59000000000000
cHNldP8BAKMCAAAAAAHHOf5Agk+E/oS33Ib0PZ+ZVsBNFGG63fEDP1ld0TZ7xgAAAAAA/f///wIBIw9PXUt8b6hFgG7k9ncTRZ4baejmD87i5JQMeg1d4bIBAAAAAAAABOgAF6kUgAxzzxsHiHCLko+66AwTy97eX3iHASMPT11LfG+oRYBu5PZ3E0WeG2no5g/O4uSUDHoNXeGyAQAAAAAAAAtZAAAAAAAAAAAL/AhlbGVtZW50cwYhA0OwH8krCdlceRfB8cKCM916EYbXdnA+bm3SZzLiC0ThAAA=
```

Blind it

```
elements-cli blindpsbt cHNldP8BAKMCAAAAAAHHOf5Agk+E/oS33Ib0PZ+ZVsBNFGG63fEDP1ld0TZ7xgAAAAAA/f///wIBIw9PXUt8b6hFgG7k9ncTRZ4baejmD87i5JQMeg1d4bIBAAAAAAAABOgAF6kUgAxzzxsHiHCLko+66AwTy97eX3iHASMPT11LfG+oRYBu5PZ3E0WeG2no5g/O4uSUDHoNXeGyAQAAAAAAAAtZAAAAAAAAAAAL/AhlbGVtZW50cwYhA0OwH8krCdlceRfB8cKCM916EYbXdnA+bm3SZzLiC0ThAAA=
cHNldP8BAKMCAAAAAAHHOf5Agk+E/oS33Ib0PZ+ZVsBNFGG63fEDP1ld0TZ7xgAAAAAA/f///wIBIw9PXUt8b6hFgG7k9ncTRZ4baejmD87i5JQMeg1d4bIBAAAAAAAABOgAF6kUgAxzzxsHiHCLko+66AwTy97eX3iHASMPT11LfG+oRYBu5PZ3E0WeG2no5g/O4uSUDHoNXeGyAQAAAAAAAAtZAAAAAAAAAAAAAA==
```

Try to sign it:

```
elements-cli walletsignpsbt cHNldP8BAKMCAAAAAAHHOf5Agk+E/oS33Ib0PZ+ZVsBNFGG63fEDP1ld0TZ7xgAAAAAA/f///wIBIw9PXUt8b6hFgG7k9ncTRZ4baejmD87i5JQMeg1d4bIBAAAAAAAABOgAF6kUgAxzzxsHiHCLko+66AwTy97eX3iHASMPT11LfG+oRYBu5PZ3E0WeG2no5g/O4uSUDHoNXeGyAQAAAAAAAAtZAAAAAAAAAAAAAA==
error code: -25
error message:
Missing UTXOs that are needed to check transaction balance
```

Decode it:

```
elements-cli decodepsbt cHNldP8BAKMCAAAAAAHHOf5Agk+E/oS33Ib0PZ+ZVsBNFGG63fEDP1ld0TZ7xgAAAAAA/f///wIBIw9PXUt8b6hFgG7k9ncTRZ4baejmD87i5JQMeg1d4bIBAAAAAAAABOgAF6kUgAxzzxsHiHCLko+66AwTy97eX3iHASMPT11LfG+oRYBu5PZ3E0WeG2no5g/O4uSUDHoNXeGyAQAAAAAAAAtZAAAAAAAAAAAAAA==
{
"tx": {
"txid": "58f50ab2318eeb6d7247de5d74f6e2b43a1a6d504ad09fd37a58d23c06876a4b",
"hash": "58f50ab2318eeb6d7247de5d74f6e2b43a1a6d504ad09fd37a58d23c06876a4b",
"wtxid": "58f50ab2318eeb6d7247de5d74f6e2b43a1a6d504ad09fd37a58d23c06876a4b",
"withash": "f150819cebd18e742bd70158fbf154dc6ca75b445141c87e8492bf48b758e628",
"version": 2,
"size": 163,
"vsize": 163,
"weight": 652,
"locktime": 0,
"vin": [
{
"txid": "c67b36d15d593f03f1ddba61144dc056999f3df486dcb784fe844f8240fe39c7",
"vout": 0,
"scriptSig": {
"asm": "",
"hex": ""
},
"is_pegin": false,
"sequence": 4294967293
}
],
"vout": [
{
"value": 0.00001256,
"asset": "b2e15d0d7a0c94e4e2ce0fe6e8691b9e451377f6e46e8045a86f7c4b5d4f0f23",
"commitmentnonce": "",
"commitmentnonce_fully_valid": false,
"n": 0,
"scriptPubKey": {
"asm": "OP_HASH160 800c73cf1b0788708b928fbae80c13cbdede5f78 OP_EQUAL",
"hex": "a914800c73cf1b0788708b928fbae80c13cbdede5f7887",
"reqSigs": 1,
"type": "scripthash",
"addresses": [
"XP2JFuUmgaeMfCqHazL2WtsKhp9fVhondp"
]
}
},
{
"value": 0.00002905,
"asset": "b2e15d0d7a0c94e4e2ce0fe6e8691b9e451377f6e46e8045a86f7c4b5d4f0f23",
"commitmentnonce": "",
"commitmentnonce_fully_valid": false,
"n": 1,
"scriptPubKey": {
"asm": "",
"hex": "",
"type": "fee"
}
}
]
},
"fees": {
"bitcoin": 0.00002905
},
"unknown": {
},
"inputs": [
{
}
],
"outputs": [
{
},
{
}
]
}
```

Tái hiện chuỗi bằng elements-cli: createrawtransaction, fundrawtransaction, converttopsbt, blindpsbt và walletsignpsbt. So sánh giao dịch đã được cấp vốn và PSBT đã giải mã, sau đó xác minh rằng kết quả có thể được làm mù và được wallet ký mà không gặp lỗi “Missing UTXOs”.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.