Do not crash on invalid callback name

client/gui/InterfaceObjectConfigurable.cpp

@@ -297,7 +297,14 @@ std::shared_ptr<CToggleButton> InterfaceObjectConfigurable::buildToggleButton(co
 		button->setImageOrder(imgOrder[0].Integer(), imgOrder[1].Integer(), imgOrder[2].Integer(), imgOrder[3].Integer());
 	}
 	if(!config["callback"].isNull())
-		button->addCallback(callbacks.at(config["callback"].String()));
+	{
+		std::string callbackName = config["callback"].String();
+
+		if (callbacks.count(callbackName))
+			button->addCallback(callbacks.at(callbackName));
+		else
+			logGlobal->error("Invalid callback '%s' in widget", callbackName );
+	}
 	return button;
 }