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": { ...
#include <key_io.h>
#include <keystore.h>
#include <rpc/util.h>
#include <tinyformat.h>
#include <util/strencodings.h>
InitInterfaces* g_rpc_interfaces = nullptr;
CPubKey HexToPubKey(const std::string& hex_in)