Tests: Fix WML tests.

Display no longer tries to draw or make buttons when it doesn't have
a screen, and the request for an empty theme name is treated as a
request for the default theme.

src/display.cpp

@@ -895,6 +895,10 @@ const std::string& get_direction(std::size_t n)
 
 void display::create_buttons()
 {
+	if(screen_.faked()) {
+		return;
+	}
+
 	menu_buttons_.clear();
 	action_buttons_.clear();
 
@@ -2054,7 +2058,7 @@ bool display::tile_nearly_on_screen(const map_location& loc) const
 void display::scroll_to_xy(int screenxpos, int screenypos, SCROLL_TYPE scroll_type, bool force)
 {
 	if(!force && (view_locked_ || !preferences::scroll_to_action())) return;
-	if(screen_.update_locked()) {
+	if(screen_.update_locked() || screen_.faked()) {
 		return;
 	}
 	const SDL_Rect area = map_area();
@@ -2414,7 +2418,7 @@ void display::draw(bool update, bool force)
 {
 	//	log_scope("display::draw");
 
-	if(screen_.update_locked()) {
+	if(screen_.update_locked() || screen_.faked()) {
 		return;
 	}
 

src/theme.cpp

@@ -1008,7 +1008,10 @@ const config& theme::get_theme_config(const std::string& id)
 		return iter->second;
 	}
 
-	ERR_DP << "Theme '" << id << "' not found. Falling back to default theme." << std::endl;
+	if (!id.empty()) { // (treat empty id as request for default theme)
+		ERR_DP << "Theme '" << id << "' not found."
+		       << " Falling back to default theme." << std::endl;
+	}
 
 	iter = known_themes.find("Default");
 	if(iter != known_themes.end()) {