Send tabs from the background to sidebar pages whether they are detec…

…ted as opened or not #2200

webextensions/background/background.js

@@ -159,11 +159,10 @@ async function notifyReadyToSidebars() {
   log('notifyReadyToSidebars: start');
   const promisedResults = [];
   for (const window of TabsStore.windows.values()) {
-    // Skip windows already detected as "opened", because the "opened" status
-    // means that the connection is estabilished and there is no need to
-    // receive tabs exported at here.
-    if (SidebarConnection.isOpen(window.id))
-      continue;
+    // Send PING to all windows whether they are detected as "opened" or "not opened yet",
+    // because the connection may be established before this background page starts listening
+    // of messages from sidebar pages.
+    // See also: https://github.com/piroor/treestyletab/issues/2200
     TabsUpdate.completeLoadingTabs(window.id); // failsafe
     log(`notifyReadyToSidebars: to ${window.id}`);
     promisedResults.push(browser.runtime.sendMessage({