How does the wallet node get the unspent list？

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### Describe the issue

### Can you reliably reproduce the issue?
#### If so, please list the steps to reproduce below:
1. The bch node is installed, and it is normally synchronized to the latest
2. Import bch address
3. Get query wallet UTXO is null

### Expected behaviour
Tell us what should happen

### Actual behaviour
Tell us what happens instead

### Screenshots.
If the issue is related to the GUI, screenshots can be added to this issue via drag & drop.

### What version of bitcoin-abc are you using?
List the version number/commit ID, and if it is an official binary, self compiled or a distribution package such as PPA.

### Machine specs:
- OS:
- CPU:
- RAM:
- Disk size:
- Disk Type (HD/SDD):

### Any extra information that might be useful in the debugging process.
This is normally the contents of a `debug.log` or `config.log` file. Raw text or a link to a pastebin type site are preferred.

The issue names no source file, test, version, or diagnostic output. Start by reproducing the listed steps on a synchronized node and trace the wallet UTXO query for the imported address; done means identifying why the result is null and confirming the expected result with a focused regression test.

Written by the indexing model from the issue text.