Remove old using statements from when Diff.cs owned the diff handle

Author: niik

LibGit2Sharp/Diff.cs

@@ -350,10 +350,17 @@ public virtual T Compare<T>(Tree oldTree, DiffTargets diffTargets, IEnumerable<s
                 }
             }
 
-            using (DiffSafeHandle diff = BuildDiffList(oldTreeId, null, comparer, diffOptions, paths, explicitPathsOptions, compareOptions))
+            DiffSafeHandle diff = BuildDiffList(oldTreeId, null, comparer, diffOptions, paths, explicitPathsOptions, compareOptions);
+            
+            try
             {
                 return BuildDiffResult<T>(diff);
             }
+            catch
+            {
+                diff.SafeDispose();
+                throw;
+            }
         }
 
         /// <summary>
@@ -469,10 +476,17 @@ internal virtual T Compare<T>(
                 }
             }
 
-            using (DiffSafeHandle diff = BuildDiffList(null, null, comparer, diffOptions, paths, explicitPathsOptions, compareOptions))
+            DiffSafeHandle diff = BuildDiffList(null, null, comparer, diffOptions, paths, explicitPathsOptions, compareOptions);
+
+            try
             {
                 return BuildDiffResult<T>(diff);
             }
+            catch
+            {
+                diff.SafeDispose();
+                throw;
+            }
         }
 
         internal delegate DiffSafeHandle TreeComparisonHandleRetriever(ObjectId oldTreeId, ObjectId newTreeId, GitDiffOptions options);