fix the build on linux. Apparently

  condition ? wxString(something) : wxEmptyString
doesn't work, because wxEmptyString is a wxChar*, and g++ doesn't see the conversion.

src/cli/text_io_handler.cpp

@@ -57,7 +57,7 @@ void TextIOHandler::init() {
 		// Use console mode if one of the cli flags is passed
 		static const Char* redirect_flags[] = {_("-?"),_("--help"),_("-v"),_("--version"),_("--cli"),_("-c"),_("--export"),_("--export-images"),_("--create-installer")};
 		for (int i = 1 ; i < wxTheApp->argc ; ++i) {
-			for (int j = 0 ; j < sizeof(redirect_flags)/sizeof(redirect_flags[0]) ; ++j) {
+			for (size_t j = 0 ; j < sizeof(redirect_flags)/sizeof(redirect_flags[0]) ; ++j) {
 				if (String(wxTheApp->argv[i]) == redirect_flags[j]) {
 					have_console = true;
 					have_stderr = true;

src/main.cpp

@@ -271,7 +271,7 @@ int MSE::OnRun() {
 					String export_template = args[1];
 					ExportTemplateP exp = package_manager.open<ExportTemplate>(export_template);
 					SetP set = import_set(args[2]);
-					String out = args.size() >= 4 ? args[3] : wxEmptyString;
+					String out = args.size() >= 4 ? args[3] : _("");
 					ScriptValueP result = export_set(set, set->cards, exp, out);
 					if (out.empty()) {
 						cli << result->toString();