[Update] Plugins: Add error handlings when network is not connected and failed to fetch plugins info.

Also add pending ui(TMP) while fetching.

src-ui/app/config_page/setting_section/setting_box/plugins/Plugins.jsx

@@ -33,6 +33,7 @@ const PluginDownloadContainer = () => {
         currentSavedPluginsStatus,
         toggleSavedPluginsStatus,
         handlePendingPlugin,
+        currentFetchedPluginsInfo,
     } = usePlugins();
     const { showNotification_Success, showNotification_Error } = useNotificationStatus();
 
@@ -65,8 +66,14 @@ const PluginDownloadContainer = () => {
         a.plugin_id.localeCompare(b.plugin_id)
     );
 
+    // Duplicate
+    const is_failed_to_fetch = currentFetchedPluginsInfo.state === "error";
+    const is_fetching = currentFetchedPluginsInfo.state === "pending";
+
     return (
         <div className={styles.plugins_list_container}>
+            {is_failed_to_fetch && <p>Failed to fetch plugins data</p>}
+            {is_fetching && <p>Fetching plugins data...</p>}
             {sorted_plugins_data.map((plugin) => (
                 <div key={plugin.plugin_id} className={styles.plugin_wrapper}>
                     <p className={styles.title}>

src-ui/app/modal_controller/update_modal/plugins_compatibility_list/PluginCompatibilityList.jsx

@@ -9,6 +9,7 @@ export const PluginCompatibilityList = () => {
     const {
         enabledPluginsList,
         asyncFetchPluginsInfo,
+        currentFetchedPluginsInfo,
     } = usePlugins();
 
     useEffect(() => {
@@ -35,9 +36,15 @@ export const PluginCompatibilityList = () => {
 
     if (!is_any_incompatible_plugin && !is_any_compatible_plugin) return null; // This is just for safety.
 
+    // Duplicate
+    const is_failed_to_fetch = currentFetchedPluginsInfo.state === "error";
+    const is_fetching = currentFetchedPluginsInfo.state === "pending";
+
     return (
         <div className={styles.container}>
             <p className={styles.title}>使用中プラグインの互換性チェック</p>
+            {is_failed_to_fetch && <p>Failed to fetch plugins data</p>}
+            {is_fetching && <p>Fetching plugins data...</p>}
             <div className={styles.plugins_compatibility_container}>
                 {incompatible_plugins_list.map(plugin => {
                     const target_data = plugin.downloaded_plugin_info;