Fix crash if you cancel the scenario selection

src/dialogxml/dialogs/dialog.hpp

@@ -114,11 +114,22 @@ public:
 	void run(std::function<void(cDialog&)> onopen = nullptr); // cd_run_dialog
 	/// Get the result of the dialog.
 	/// @tparam type The result type.
-	/// @throw boost::bad_any_cast if the provided result type is different from the type set by getResult().
+	/// @throw boost::bad_any_cast if the provided result type is different from the type set by setResult().
 	/// @return The dialog's result.
 	template<typename type> type getResult() const {
 		return boost::any_cast<type>(result);
 	}
+	/// Check if the dialog has a result.
+	/// @return true if setResult() was called, otherwise false.
+	bool hasResult() const {
+		return !result.empty();
+	}
+	/// Query the type of the result.
+	/// @tparam type The result type to query.
+	/// @return true if the type matches that set by setResult().
+	template<typename type> bool resultIs() const {
+		return result.type() == typeid(type);
+	}
 	/// Set the result of the dialog.
 	/// @tparam type The result type.
 	/// @param val The result value.

src/game/boe.dlgutil.cpp

@@ -1508,8 +1508,6 @@ class cChooseScenario {
 	}
 
 	bool doCancel() {
-		scen_header_type null;
-		me.setResult<scen_header_type>(null);
 		me.toast(false);
 		return true;
 	}
@@ -1576,6 +1574,7 @@ public:
 		}
 		
 		me.run();
+		if(!me.hasResult()) return scen_header_type{};
 		scen_header_type scen = me.getResult<scen_header_type>();
 		if(scen.file.empty()){
 			std::ostringstream error;