enhance: avoid unhandled exceptions in timer

Signed-off-by: leo <longshuang@msn.cn>

src/ViewModels/Repository.cs

@@ -2512,6 +2512,8 @@ namespace SourceGit.ViewModels
         }
 
         private void AutoFetchImpl(object sender)
+        {
+            try
             {
                 if (!_settings.EnableAutoFetch || _isAutoFetching)
                     return;
@@ -2538,6 +2540,11 @@ namespace SourceGit.ViewModels
                 _lastFetchTime = DateTime.Now;
                 Dispatcher.UIThread.Invoke(() => IsAutoFetching = false);
             }
+            catch
+            {
+                // DO nothing, but prevent `System.AggregateException`
+            }
+        }
 
         private string _fullpath = string.Empty;
         private string _gitDir = string.Empty;