Currently, we use `assert` in RPC code to document logic and code assumptions. However, it seems a bit extreme to abort all of Bitcoin Core on an assert failure in one of the RPC threads. I suggest to replace all checks with a macro `THROW_LOGIC_ERROR_IF_ASSERT_FAILS(condition)` that does what it says. That logic error will then be returned to the rpc caller and will include instructions to report the error to our issue tracker.

Any objections or naming suggestions for that macro?
!index->LookupFilterHeader(block_index, filter_header)) {
        int err_code;
        std::string errmsg = "Filter not found.";
        if (!block_was_connected) {
            err_code = RPC_INVALID_ADDRESS_OR_KEY;
            errmsg += " Block was not connected to active chain.";
        } else if (!index_ready) {
            err_code = RPC_MISC_ERROR;
            errmsg += " Block filters are still in the process of being indexed.";
        } else {
            err_code = RPC_INTERNAL_ERROR;
            errmsg += " This error is unexpected and indicates index corruption.";
        }
        throw JSONRPCError(err_code, errmsg);
    }
    UniValue ret(UniValue::VOBJ);
    ret.pushKV("filter", HexStr(filter.GetEncodedFilter()));
    ret.pushKV("header", filter_header.GetHex());
    return ret;
}
static const CRPCCommand commands[] =
{ 
  
    { "blockchain",         "getblockchaininfo",      &getblockchaininfo,      {} },
    { "blockchain",         "getchaintxstats",        &getchaintxstats,        {"nblocks", "blockhash"} },
    { "blockchain",         "getblockstats",          &getblockstats,          {"hash_or_height", "stats"} },
    { "blockchain",         "getbestblockhash",       &getbestblockhash,       {} },
    { "blockchain",         "getblockcount",          &getblockcount,          {} },
    { "blockchain",         "getblock",               &getblock,               {"blockhash","verbosity|verbose"} },
    { "blockchain",         "getblockhash",           &getblockhash,           {"height"} },