Fix of 2.3 rc1 can't load its own 3mf files (if they contain custom gcode) #5550

The issue was handling of the special "default_filament_profile" vector,
which is not being normalized in length to the number of extruders,
as this vector is being shown to the user at the Printer dependencies page,
and we don't want to present empty fields there, if the default filament
profile was not defined in the system preset.

src/libslic3r/PrintConfig.cpp

@@ -3378,6 +3378,8 @@ void DynamicPrintConfig::set_num_extruders(unsigned int num_extruders)
     const auto &defaults = FullPrintConfig::defaults();
     for (const std::string &key : print_config_def.extruder_option_keys()) {
         if (key == "default_filament_profile")
+            // Don't resize this field, as it is presented to the user at the "Dependencies" page of the Printer profile and we don't want to present
+            // empty fields there, if not defined by the system profile.
             continue;
         auto *opt = this->option(key, false);
         assert(opt != nullptr);