Fix for crash from #7486 - PrusaSlicer crashes when doing this commands

src/slic3r/GUI/OptionsGroup.hpp

@@ -181,6 +181,8 @@ public:
     // we have to set same max contrtol width to all of them
 	void				set_max_win_width(int max_win_width);
 
+	bool				is_activated() { return sizer != nullptr; }
+
 protected:
 	std::map<t_config_option_key, Option>	m_options;
     wxWindow*				m_parent {nullptr};

src/slic3r/GUI/Tab.cpp

@@ -3933,6 +3933,8 @@ bool Tab::validate_custom_gcodes()
     bool valid = true;
     for (auto opt_group : m_active_page->m_optgroups) {
         assert(opt_group->opt_map().size() == 1);
+        if (!opt_group->is_activated())
+            break;
         std::string key = opt_group->opt_map().begin()->first;
         valid &= validate_custom_gcode(opt_group->title, boost::any_cast<std::string>(opt_group->get_value(key)));
         if (!valid)