Made spec_sort specifications featuring more than one '()' not hang.

Added error window if a script error occurs while loading a set.

src/gui/new_window.cpp

@@ -91,10 +91,15 @@ void NewSetWindow::OnOK(wxCommandEvent&) {
 }
 
 void NewSetWindow::done() {
+	try {
 	StyleSheetP stylesheet = stylesheet_list->getSelection<StyleSheet>();
 	set = new_intrusive1<Set>(stylesheet);
 	set->validate();
 	EndModal(wxID_OK);
+	} catch (Error& e) {
+	handle_error(e);
+	throw; // We want to crash.
+	}
 }
 
 void NewSetWindow::onUpdateUI(wxUpdateUIEvent& ev) {

src/script/functions/basic.cpp

@@ -510,7 +510,7 @@ String spec_sort(const String& spec, const String& input) {
 			pos = end;
 			
 		} else if (c == _('(')) {	// in a cycle
-			size_t end = spec.find_first_of(_(')'));
+			size_t end = spec.find_first_of(_(')'), pos);
 			if (end == String::npos) throw ParseError(_("Expected ')' in sort_rule specification"));
 			ret += cycle_sort(spec.substr(pos + 1, end - pos - 1), input);
 			pos = end;