The importmulti help text reads, in part: 

```
{                                                          (json object) If a ranged descriptor is used, this specifies the start and end of the range to import
           "start": n,                                              (numeric, optional, default=0) Start of the range to import
           "end": n,                                                (numeric, required) End of the range to import (inclusive)
},
```

This is a value for which a key is missing; it should be "range": { ...
{
public:
    explicit DescribeAddressVisitor() {}
    UniValue operator()(const CNoDestination& dest) const
    {
        return UniValue(UniValue::VOBJ);
    }
    UniValue operator()(const CKeyID& keyID) const
    {
        UniValue obj(UniValue::VOBJ);
        obj.pushKV("isscript", false);
        obj.pushKV("iswitness", false);
        return obj;
    }
    UniValue operator()(const CScriptID& scriptID) const
    {
        UniValue obj(UniValue::VOBJ);
        obj.pushKV("isscript", true);
        obj.pushKV("iswitness", false);
        return obj;
    }
    UniValue operator()(const WitnessV0KeyHash& id) const