message: fix div by zero in cpu usage
diff: @@ -332,7 +332,7 @@ int64_t resource_limits_manager::get_account_cpu_limit( const account_name& name
  int64_t cpu_weight;
  get_account_limits( name, unused, unused, cpu_weight );
  - if( cpu_weight < 0 ) {
  + if( cpu_weight < 0 || state.total_cpu_weight == 0 ) {
  return -1;
  }
  