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": { ...
{
    
    if (required < 1) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, "a multisignature address must require at least one key to redeem");
    }
    if ((int)pubkeys.size() < required) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("not enough keys supplied (got %u keys, but need at least %d to redeem)", pubkeys.size(), required));
    }
    if (pubkeys.size() > 16) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Number of keys involved in the multisignature address creation > 16\nReduce the number");
    }
    CScript result = GetScriptForMultisig(required, pubkeys);
    if (result.size() > MAX_SCRIPT_ELEMENT_SIZE) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, (strprintf("redeemScript exceeds size limit: %d > %d", result.size(), MAX_SCRIPT_ELEMENT_SIZE)));
    }
    return result;
}
class DescribeAddressVisitor : public boost::static_visitor<UniValue>