get_ops_in_block return empty results for no irreversible block

[oflyhigh]

get_ops_in_block API for head block or block which number > last_irreversible_block_num, it returned empty results.

Steps:

• get the head_block_number

{"jsonrpc": "2.0", "method": "condenser_api.get_dynamic_global_properties", "params": [], "id": 1}

• call get_ops_in_block with head_block_number immediately. where xxxx is the head_block_number

{"jsonrpc": "2.0", "method": "condenser_api.get_ops_in_block", "params": [xxxx], "id": 1}

Results:

{'id': 1, 'jsonrpc': '2.0', 'result': []}

If this is what it should be, I think it should be better to mark this API get_ops_in_block can only apply to irreversible block in documents.