Check block height does not progress from 0
Hello, I am working on openmonero with docker-compose backend.
I set up monero, mysql, openmonero, and lighttpd on separate containers, connecting each successfully with connection and directory sharing.

I use monero version v0.12.0.0 for monero and openmonero setup.

Blockchain data was collected and verified by the latest version of v0.12.3.0 fullnode, and later copied for the purpose of usage in openmonero project.
I am running server on mainnet, and the frontend lighttpd seems to be working.

However, after I successfully generated address and tried to import recent transactions, I found unexpected error:

```
$ curl 'http://x.y.z.w:1984/import_recent_wallet_request'  --data '{"address":"4BCr8KnNSRWC2dxa9SvXD8CQMSVHGxKNBBf3KYm7GLhyhTvZ8snqiQJhRQbdCuWwi48CYEkaVLBNs282mCcUN7vBFkABfMN","view_key":"b750a20f39cd2b50ff810b0d50e59961071d5f472d3e6819330ffe1c8a8d110f","no_blocks_to_import":"1000"}' ; echo 
{"request_fulfilled":false}
```

There's no information on why the request is not fulfilled. It seems that these two if statement in YourMoneroRequests.cpp do not have error handling and causing this strange error.

https://github.com/moneroexamples/openmonero/blob/master/src/YourMoneroRequests.cpp#L1131-L1138

On server backend, there's also no obvious error messages available. It only continues a lot of following messages

```

get_output_keys: Attempting to get output pubkey by global index (amount 0, index 1307405, count 0), but key does not exist (current height 1)
Mixins key images not found
get_output_keys: Attempting to get output pubkey by global index (amount 0, index 3104011, count 0), but key does not exist (current height 1)
Mixins key images not found
get_output_keys: Attempting to get output pubkey by global index (amount 0, index 2269153, count 0), but key does not exist (current height 1)
Mixins key images not found
get_output_keys: Attempting to get output pubkey by global index (amount 0, index 4340498, count 0), but key does not exist (current height 1)
Mixins key images not found
Check block height: 0 no of mempool txs: 78
Thread exists, dont make new one
Search thread started
new last_ping_timestamp: 1535275386

```

So, it seems the error is about that backend is not syncing well with monero daemon.
I already tried stdin_open: true in docker-compose yml file.

How can I properly sync my backend and check block height?