<fix>[errorcode]: address review — null-safe message fallback and avoid loader init

- GlobalErrorCodeI18nServiceImpl: add final fallback to error.code/empty string
  when both details and description are null, guaranteeing message is never null
- Platform: use existing loader field instead of getComponentLoader() to avoid
  triggering ComponentLoader creation during early startup; move message fallback
  outside catch block so it always runs

Co-Authored-By: ye.zou <ye.zou@zstack.io>

Change-Id: I8571f05657dc2173cc232b511f505eedc68d714e

Author: AlanJager

core/src/main/java/org/zstack/core/Platform.java

@@ -992,15 +992,18 @@ public static ErrorCode err(String globalErrorCode, Enum errCode, ErrorCode caus
         // populate message at creation time with default locale;
         // RestServer will override with client's Accept-Language if different
         try {
-            GlobalErrorCodeI18nService i18nService = getComponentLoader().getComponent(GlobalErrorCodeI18nService.class);
-            if (i18nService != null) {
-                i18nService.localizeErrorCode(result, org.zstack.core.errorcode.LocaleUtils.DEFAULT_LOCALE);
+            ComponentLoader currentLoader = loader;
+            if (currentLoader != null) {
+                GlobalErrorCodeI18nService i18nService = currentLoader.getComponent(GlobalErrorCodeI18nService.class);
+                if (i18nService != null) {
+                    i18nService.localizeErrorCode(result, org.zstack.core.errorcode.LocaleUtils.DEFAULT_LOCALE);
+                }
             }
         } catch (Exception e) {
-            // i18n service not initialized during early startup, use details as fallback
-            if (result.getMessage() == null) {
-                result.setMessage(details);
-            }
+            // i18n service not initialized during early startup
+        }
+        if (result.getMessage() == null) {
+            result.setMessage(details != null ? details : result.getDescription());
         }
 
         return result;

core/src/main/java/org/zstack/core/errorcode/GlobalErrorCodeI18nServiceImpl.java

@@ -140,7 +140,8 @@ public void localizeErrorCode(ErrorCode error, String locale) {
 
         // guarantee: message is never null
         if (error.getMessage() == null) {
-            error.setMessage(error.getDetails() != null ? error.getDetails() : error.getDescription());
+            String fallback = error.getDetails() != null ? error.getDetails() : error.getDescription();
+            error.setMessage(fallback != null ? fallback : (error.getCode() != null ? error.getCode() : ""));
         }
 
         if (error.getCause() != null) {