Skip REST call when event buffer is empty

[samssh]

Hi Langfuse team,

While using the Go SDK I noticed that the client still performs a REST call on every flush interval even when there are no events queued. Because the body is an empty JSON object/array, the request has no functional effect but still:

• Generates unnecessary network traffic and latency

• Adds noise to access/error logs

• Counts toward any rate limits or request-based billing