starknet_syncing returning null if first block not synced

[stdevMac]

Describe the bug When the node starts to run for the first time, when called the method starknet_syncing, it will try to ask for block information that isn't yet on the database, so, it will return nil.

To Reproduce Steps to reproduce the behavior:

1. Run the node
2. Before syncing the first block information, call method starknet_syncing
3. Receive nil

Expected behavior Return an empty response on those fields