fix: app crashed after enable Show children in the commit details (#1072)

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

Author: love-linger

src/Commands/QueryCommitChildren.cs

@@ -12,7 +12,7 @@ public QueryCommitChildren(string repo, string commit, int max)
             Args = $"rev-list -{max} --parents --branches --remotes ^{commit}";
         }
 
-        public IEnumerable<string> Result()
+        public List<string> Result()
         {
             Exec();
             return _lines;

src/ViewModels/CommitDetail.cs

@@ -615,7 +615,7 @@ private void Refresh()
                     var cmdChildren = new Commands.QueryCommitChildren(_repo.FullPath, _commit.SHA, max) { Cancel = _cancelToken };
                     var children = cmdChildren.Result();
                     if (!cmdChildren.Cancel.Requested)
-                        Dispatcher.UIThread.Post(() => Children.AddRange(children));
+                        Dispatcher.UIThread.Post(() => Children = children);
                 });
             }