TraceSet is interpreted incorrectly if no data is specified

[Siebje]

To reproduce:

• Create an empty trace set with the header containing only Header.TRS_VERSION: 2
• Try to open the trace set

Expected:

• The trace set can be opened

Actual: [ERROR] 13:59:31 FIPy base_request_handler.py:_handle_request_exception:43 | Traceback (most recent call last): [...] File "\trsfile\engine\trs.py", line 301, in get_traces parameters = self.read_parameter_data() File "\trsfile\engine\trs.py", line 323, in read_parameter_data parameters['LEGACY_DATA'] = ByteArrayParameter(data) File "\trsfile\traceparameter.py", line 23, in init raise ValueError('The value for a TraceParameter cannot be empty')