RulesState::defaultVariables called needlessly

In the hunt for the cause of #1322682: Many conditions may result in memory crashes? I noticed that RulesState::defaultVariables looks like is being called multiple times needlessly in includes/rules.core.inc.

Was:

public function availableVariables() {
  $vars = RulesState::defaultVariables();
  return !$this->isRoot() ? $this->parent->stateVariables($this) : $vars;
}

Changed to:

public function availableVariables() {
  return !$this->isRoot() ? $this->parent->stateVariables($this) : RulesState::defaultVariables();
}

Which should mean that RulesState::defaultVariables() is only ever called when $this->isRoot is TRUE, and not every single time availableVariables() is called.