XLS - Fix adding cell comment

main/HSSF/Record/EscherAggregate.cs

@@ -1298,10 +1298,7 @@ public void RemoveTailRecord(NoteRecord note)
 
         internal void AddTailRecord(NoteRecord note)
         {
-            if (tailRec.ContainsKey(note.ShapeId))
-                tailRec.Add(note.ShapeId, note);
-            else
-                tailRec[note.ShapeId] = note;
+            tailRec[note.ShapeId] = note;
         }
         /**
      * @return unmodifiable copy of tail records. We need to access them when building shapes.

testcases/main/HSSF/UserModel/TestHSSFComment.cs

@@ -452,5 +452,20 @@ public void ShapeId()
 
             wb.Close();
         }
+
+        [Test]
+        public void TestBug1240()
+        {
+            using(var wb = HSSFTestDataSamples.OpenSampleWorkbook("test_FailAddingComment.xls"))
+            {
+                Assert.DoesNotThrow(() =>
+                {
+                    ISheet sheet = wb.GetSheetAt(0);
+                    var drawingPatriarch2 = sheet.CreateDrawingPatriarch();
+                    IClientAnchor anchor2 = drawingPatriarch2.CreateAnchor(0, 0, 0, 0, 55, 71, 58, 75);
+                    IComment comment2 = drawingPatriarch2.CreateCellComment(anchor2);
+                });
+            }
+        }
     }
 }