Fix: TextfileWindow called virtual methods before constructor completed. (#11889)

SetStringParameters() was called during widget tree init in the constructor.

Calls within a constructor cannot call the derived classes methods. This would result in invalid data being passed to the string system, which could then crash.

(cherry picked from commit fef0bfcfd3)

src/network/network_gui.cpp

@@ -2571,6 +2571,8 @@ struct SurveyResultTextfileWindow : public TextfileWindow {
 
 	SurveyResultTextfileWindow(TextfileType file_type) : TextfileWindow(file_type)
 	{
+		this->ConstructWindow();
+
 		auto result = _survey.CreatePayload(NetworkSurveyHandler::Reason::PREVIEW, true);
 		this->LoadText(result);
 		this->InvalidateData();