fix: System.ArgumentException when hover the commit link multiple times before the first time tooltip shows (#765)

src/ViewModels/CherryPick.cs

@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using System.Text;
 using System.Threading.Tasks;
 
 namespace SourceGit.ViewModels

src/Views/CommitMessagePresenter.cs

@@ -296,7 +296,8 @@ namespace SourceGit.Views
                         if (currentParent is { DataContext: ViewModels.CommitDetail currentDetail } &&
                             currentDetail.Commit.SHA == lastDetailCommit)
                         {
-                            _inlineCommits.Add(sha, c);
+                            if (!_inlineCommits.ContainsKey(sha))
+                                _inlineCommits.Add(sha, c);
 
                             // Make sure user still hovers the target SHA.
                             if (_lastHover == link && c != null)