Fix e49150f9ca: House picker crashes if selection is not available.

This occurs because the extra invalidation in OnInit() also happens on construction, and too early.

Solution is to validate all instead of just position when invalidating in OnInit().

src/town_gui.cpp

@@ -1743,7 +1743,7 @@ struct BuildHouseWindow : public PickerWindow {
 
 	void OnInit() override
 	{
-		this->InvalidateData(PickerInvalidation::Position);
+		this->InvalidateData(PICKER_INVALIDATION_ALL);
 		this->PickerWindow::OnInit();
 	}