Report ID (rptID) should not be empty

[BurTah00]

According to:

iec61850-7-2-ed2: 17.2.2.4 RptID - report identifier

The attribute defines the client-specified report identifier that has caused the generation of the report.

(warning) If the report identifier value is NULL, then the (mms) reference of the BRCB shall be reported as the report identifier (note: according to iec61850-8-1 this applies for report services in general (BRCB and URCB))

OpenSCD leaves rptID by default empty.

When the SCL file exported with empty rptID is imported to SIEMENS SysConf: it fails because of MinLength.

In SIEMENS SysConf, rptID comes by default with CB Reference, if not modified later;

This implementation is same in ABB.

Proposal: Apply the same behaviour; if rptID is empty, fill it with CB Ref by default.