message: core: don't copy garbage from mavlink message
  There can be potential garbage after the zero termination that we don't
  want to copy over.
  This caused segfaults during the calibration where multi chunk
  statustexts are used.
diff: @@ -250,7 +250,7 @@ void SystemImpl::process_statustext(const mavlink_message_t& message)
  // statustext.text is not null terminated, therefore we copy it first to
  // an array big enough that is zeroed.
  char text_with_null[sizeof(statustext.text) + 1]{};
  - memcpy(text_with_null, statustext.text, sizeof(statustext.text));
  + strncpy(text_with_null, statustext.text, sizeof(text_with_null) - 1);
  // Only use the debug string for the first chunk of the sequence
  // or if there is just one message in the sequence
  