set fallbackDate to useSWRxSlackChannels

packages/app/src/components/Page.jsx

@@ -210,7 +210,7 @@ const PageWrapper = (props) => {
       isGuestUser={isGuestUser}
       isMobile={isMobile}
       isSlackEnabled={isSlackEnabled || false}
-      slackChannels={slackChannelsData?.toString() || ''}
+      slackChannels={slackChannelsData.toString()}
       grant={grant}
       grantGroupId={grantGroupId}
       grantGroupName={grantGroupName}

packages/app/src/components/PageEditor.jsx

@@ -428,7 +428,7 @@ const PageEditorWrapper = (props) => {
       editorMode={editorMode}
       isMobile={isMobile}
       isSlackEnabled={isSlackEnabled || false}
-      slackChannels={slackChannelsData?.toString() || ''}
+      slackChannels={slackChannelsData.toString()}
       grant={grant}
       grantGroupId={grantGroupId}
       grantGroupName={grantGroupName}

packages/app/src/components/PageEditorByHackmd.jsx

@@ -445,7 +445,7 @@ const PageEditorByHackmdWrapper = (props) => {
       {...props}
       editorMode={editorMode}
       isSlackEnabled={isSlackEnabled || false}
-      slackChannels={slackChannelsData?.toString() || ''}
+      slackChannels={slackChannelsData.toString()}
       grant={grant}
       grantGroupId={grantGroupId}
       grantGroupName={grantGroupName}

packages/app/src/stores/editor.tsx

@@ -80,6 +80,7 @@ export const useSWRxSlackChannels = (): SWRResponse<Nullable<string[]>, Error> =
   return useSWR(
     shouldFetch ? ['/pages.updatePost', currentPagePath] : null,
     (endpoint, path) => apiGet(endpoint, { path }).then((response: SlackChannels) => response.updatePost),
+    { fallbackData: [''] },
   );
 };