Segfault when (thread) CounterStats is called with empty vector

[ahueck]

The segfault happens, if the Runtime is instantiated (and then discarded) by calling only the API that does not mutate the AccessCounter during execution, e.g.,

int main(int argc, char** argv) {
  const void* ret_check=NULL;
  const void* addr = 1;
  typeart_get_return_address(addr, &ret_check);
  return 0;
}

Defect

CounterStats::create -> vals is empty, the following code causes the segfault:

    Counter min  = *std::min_element(vals.begin(), vals.end());
    Counter max  = *std::max_element(vals.begin(), vals.end());