Async invoke fixes and ButtonGrid update

- removing unused imports
- adding null check for async handler invokes
- fixing PageCount calculation on ButtonGrid

TelegramBotBase/Controls/Hybrid/ButtonGrid.cs

@@ -149,7 +149,10 @@ namespace TelegramBotBase.Controls.Hybrid
 
         public async Task OnButtonClicked(ButtonClickedEventArgs e)
         {
-            var handler = this.Events[__evButtonClicked].GetInvocationList().Cast<AsyncEventHandler<ButtonClickedEventArgs>>();
+            var handler = this.Events[__evButtonClicked]?.GetInvocationList().Cast<AsyncEventHandler<ButtonClickedEventArgs>>();
+            if (handler == null)
+                return;
+
             foreach (var h in handler)
             {
                 await Async.InvokeAllAsync<ButtonClickedEventArgs>(h, this, e);

TelegramBotBase/Controls/Hybrid/MultiView.cs

@@ -6,7 +6,6 @@ using System.Text;
 using System.Threading.Tasks;
 using TelegramBotBase.Args;
 using TelegramBotBase.Base;
-using static TelegramBotBase.Base.Async;
 
 namespace TelegramBotBase.Controls.Hybrid
 {

TelegramBotBase/Controls/Hybrid/TaggedButtonGrid.cs

@@ -160,7 +160,10 @@ namespace TelegramBotBase.Controls.Hybrid
 
         public async Task OnButtonClicked(ButtonClickedEventArgs e)
         {
-            var handler = this.Events[__evButtonClicked].GetInvocationList().Cast<AsyncEventHandler<ButtonClickedEventArgs>>();
+            var handler = this.Events[__evButtonClicked]?.GetInvocationList().Cast<AsyncEventHandler<ButtonClickedEventArgs>>();
+            if (handler == null)
+                return;
+
             foreach (var h in handler)
             {
                 await Async.InvokeAllAsync<ButtonClickedEventArgs>(h, this, e);
@@ -759,7 +762,7 @@ namespace TelegramBotBase.Controls.Hybrid
                 if (bf.Rows == 0)
                     return 1;
 
-                return (int)Math.Ceiling((decimal)(bf.Rows / (decimal)(MaximumRow - 3)));
+                return (int)Math.Ceiling((decimal)(bf.Rows / (decimal)(MaximumRow - this.LayoutRows)));
             }
         }