Prevent wesnoth from crashing after campaign credits (#8235)

Fixes #7395

src/gui/dialogs/outro.cpp

@@ -36,6 +36,7 @@ outro::outro(const game_classification& info)
 	: modal_dialog(window_id())
 	, text_()
 	, current_text_()
+	, text_index_(0)
 	, duration_(info.end_text_duration)
 	, fade_step_(0)
 	, fading_in_(true)
@@ -84,7 +85,7 @@ outro::outro(const game_classification& info)
 		}
 	}
 
-	current_text_ = text_.begin();
+	current_text_ = text_[0];
 
 	if(!duration_) {
 		duration_ = 3500; // 3.5 seconds
@@ -94,11 +95,16 @@ outro::outro(const game_classification& info)
 void outro::pre_show(window& window)
 {
 	window.set_enter_disabled(true);
-	window.get_canvas(0).set_variable("outro_text", wfl::variant(*current_text_));
+	window.get_canvas(0).set_variable("outro_text", wfl::variant(current_text_));
 }
 
 void outro::update()
 {
+	// window doesn't immediately close, keep returning until it does
+	if(text_index_ >= text_.size()) {
+		return;
+	}
+
 	/* If we've faded fully in...
 	 *
 	 * NOTE: we want fading to take around half a second. Given this function runs about every 3 frames, we
@@ -118,16 +124,16 @@ void outro::update()
 
 	// If we've faded fully out...
 	if(!fading_in_ && fade_step_ < 0) {
-		std::advance(current_text_, 1);
-
 		// ...and we've just showed the last text bit, close the window.
-		if(current_text_ == text_.end()) {
+		text_index_++;
+		if(text_index_ >= text_.size()) {
 			window::close();
 			return;
 		}
+		current_text_ = text_[text_index_];
 
 		// ...else show the next bit.
-		window_canvas.set_variable("outro_text", wfl::variant(*current_text_));
+		window_canvas.set_variable("outro_text", wfl::variant(current_text_));
 
 		fading_in_ = true;
 		fade_step_ = 0;

src/gui/dialogs/outro.hpp

@@ -48,10 +48,9 @@ private:
 
 	virtual void post_show(window& window) override;
 
-	void draw_callback();
-
 	std::vector<std::string> text_;
-	std::vector<std::string>::iterator current_text_;
+	std::string current_text_;
+	std::size_t text_index_;
 
 	unsigned int duration_;
 	int fade_step_;

src/gui/widgets/window.hpp

@@ -221,8 +221,8 @@ public:
 	/**
 	 * Requests to close the window.
 	 *
-	 * At the moment the request is always honored but that might change in the
-	 * future.
+	 * This request is not always honored immediately, and so callers must account for the window remaining open.
+	 * For example, when overriding draw_manager's update() method.
 	 */
 	void close()
 	{