[KOE-67] Added offline check to periodic tasks

src/AcaciaZPushPlugin/AcaciaZPushPlugin/Stubs/IAddIn.cs

@@ -90,5 +90,7 @@ namespace Acacia.Stubs
         ISignatures GetSignatures();
 
         void InUI(Action action);
+
+        bool IsOffline { get; }
     }
 }

src/AcaciaZPushPlugin/AcaciaZPushPlugin/Stubs/OutlookWrappers/AddInWrapper.cs

@@ -68,6 +68,22 @@ namespace Acacia.Stubs.OutlookWrappers
             return new SignaturesWrapper();
         }
 
+        public bool IsOffline
+        {
+            get
+            {
+                NSOutlook.NameSpace session = _app.Session;
+                try
+                {
+                    return session.Offline;
+                }
+                finally
+                {
+                    ComRelease.Release(session);
+                }
+            }
+        }
+
         public void InUI(Action action)
         {
             Exception x = null;

src/AcaciaZPushPlugin/AcaciaZPushPlugin/ZPush/ZPushSync.cs

@@ -178,6 +178,9 @@ namespace Acacia.ZPush
         /// </summary>
         private void ExecuteTasks()
         {
+            if (ThisAddIn.Instance.IsOffline)
+                return;
+
             foreach (ZPushAccount account in _watcher.Accounts.GetAccounts())
                 ExecuteTasks(account);
         }