fix: "Cannot connect to store node" banner never disappears

connect to the correct signal

the store node (aka mailserver) is no longer a dialog that would let the
user select a new available mailserver; we care about a working and
_active_ mailserver here

Fixes #9358

src/app/modules/main/controller.nim

@@ -90,10 +90,13 @@ proc init*(self: Controller) =
     let d9 = 9*86400 # 9 days
     discard self.settingsService.setDefaultSyncPeriod(d9)
 
-  self.events.on(SIGNAL_MAILSERVER_AVAILABLE) do(e:Args):
+  self.events.on(SIGNAL_ACTIVE_MAILSERVER_CHANGED) do(e:Args):
+    let args = ActiveMailserverChangedArgs(e)
+    if args.nodeAddress == "":
+      return
     self.delegate.emitMailserverWorking()
-    echo "MAILSERVER AVAILABLE: ", repr(e)
-    # We need to take some actions here. This is the only pace where "mailserverAvailable" signal should be handled.
+    echo "ACTIVE MAILSERVER CHANGED: ", repr(e)
+    # We need to take some actions here. This is the only place where "activeMailserverChanged" signal should be handled.
     # Do the following, if we really need that.
     # requestAllHistoricMessagesResult
     # requestMissingCommunityInfos