stylesheet and export template have a dependency on the game

src/data/export_template.cpp

@@ -20,6 +20,15 @@ ExportTemplate::ExportTemplate()
 String ExportTemplate::typeNameStatic() { return _("export-template"); }
 String ExportTemplate::typeName() const { return _("export-template"); }
 
+void ExportTemplate::validate(Version) {
+	if (!game) {
+		throw Error(_ERROR_("no game specified for export template"));
+	}
+	// an export template depends on the game it is made for
+	requireDependency(game.get());
+}
+
+
 IMPLEMENT_REFLECTION(ExportTemplate) {
 	REFLECT_BASE(Packaged);
 	REFLECT(game);

src/data/export_template.hpp

@@ -35,6 +35,7 @@ class ExportTemplate : public Packaged {
 	
 	static String typeNameStatic();
 	virtual String typeName() const;
+	virtual void validate(Version = app_version);
   private:
 	DECLARE_REFLECTION();
 };

src/data/stylesheet.cpp

@@ -63,6 +63,15 @@ String StyleSheet::stylesheetName() const {
 String StyleSheet::typeNameStatic() { return _("style"); }
 String StyleSheet::typeName() const { return _("style"); }
 
+void StyleSheet::validate(Version) {
+	if (!game) {
+		throw Error(_ERROR_("no game specified for stylesheet"));
+	}
+	// a stylsheet depends on the game it is made for
+	requireDependency(game.get());
+}
+
+
 StyleP StyleSheet::styleFor(const FieldP& field) {
 	if (card_style.containsKey(field)) {
 		return card_style[field];

src/data/stylesheet.hpp

@@ -64,6 +64,8 @@ class StyleSheet : public Packaged {
 	
 	static String typeNameStatic();
 	virtual String typeName() const;
+	/// Validate the stylesheet
+	virtual void validate(Version = app_version);
 	
   protected: