Make Model an optional field for tlBMC fans

Model is not reported on all fan objects. This is not an expected field in the redfish output for GF fans. We can make this optional for some platforms

#tlbmc

PiperOrigin-RevId: 819982592
Change-Id: I07452c3118491c935326b04dcea35ebdfabf09c8
diff --git a/tlbmc/configs/entity_config_json_impl.cc b/tlbmc/configs/entity_config_json_impl.cc
index 2d41528..17265ae 100644
--- a/tlbmc/configs/entity_config_json_impl.cc
+++ b/tlbmc/configs/entity_config_json_impl.cc
@@ -2408,13 +2408,6 @@
         config.dump()));
   }
 
-  const std::string* model = GetValueAsString(config, "Model");
-  if (model == nullptr) {
-    return absl::InvalidArgumentError(absl::StrCat(
-        "Invalid config: Model field is not found for fan config: ",
-        config.dump()));
-  }
-
   const bool* is_hotpluggable = GetValueAsBool(config, "HotPluggable");
   if (is_hotpluggable == nullptr) {
     return absl::InvalidArgumentError(absl::StrCat(
@@ -2443,7 +2436,10 @@
   // Add fan to fru table.
   Fru fan_fru;
   fan_fru.mutable_data()->mutable_fan_info()->set_name(*name);
-  fan_fru.mutable_data()->mutable_fan_info()->set_model(*model);
+  const std::string* model = GetValueAsString(config, "Model");
+  if (model != nullptr) {
+    fan_fru.mutable_data()->mutable_fan_info()->set_model(*model);
+  }
   fan_fru.mutable_data()->mutable_fan_info()->set_is_hotpluggable(
       *is_hotpluggable);
   fan_fru.mutable_data()->mutable_fan_info()->set_pwm_sensor_name(