TC track forecast missing time period handling

[ThomasRoosli]

TC track forecast continue reading messages from a multimessage bufr file in case a track is missing the field timeperiod For example: the forecast of ECMWF contains a storm that is not trackable: https://charts.ecmwf.int/products/cyclone?base_time=202308220000&product=tc_strike_probability&unique_id=07L_EMILY_2023

This is represented in the bufr file by not having a timeperiod defined. In the case of a multimessage bufr file, the rest of the messages should still be read even if one track needs to be discarded. This MR fixes that behaviour and tests it with the above example. The behaviour is now the same for one multimessage bufr file and several bufr files.

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