Fix identification of identifier for error report. Setting it to null if the previous attempt was successfull already obviously was a flaw. Using the wrong key HAUPTPROBEN_NR probably could have been avoided by usage of appropriate constants.

{
    "messungsId": 1200,
    "messgroesseId": 242,
    "messwert":1,
    "messwertNwg":"",
    "messfehler":1,
    "nwgZuMesswert":3,
    "mehId":207,
    "grenzwertueberschreitung":false
}