Commented Unassigned: Comments.Remove on a cell breaks comments in same column [15549]

Version: EPPlus 4.1

After removing a comment from a cell, further accesses to comments on other cells of the same column get unexpected results: either cell.Comment returns null even if a comment is actually present, or ws.Comments.Remove(cell.Comment) throws "Comment does not exist in the worksheet" exception.

Unit tests for bug reproduction (using attached in.xslx):

```
[TestMethod]
public void BugCommentNullAfterRemove() {

string xls = "in.xlsx";

ExcelPackage theExcel = new ExcelPackage(new FileInfo(xls), true);

ExcelRangeBase cell;
ExcelComment cmnt;
ExcelWorksheet ws = theExcel.Workbook.Worksheets[1];

foreach (string addr in "B4 B11".Split(' ')) {
cell = ws.Cells[addr];
cmnt = cell.Comment;

Assert.IsNotNull(cmnt, "Comment in " + addr + " expected not null ");
ws.Comments.Remove(cmnt);
}

}

[TestMethod]
public void BugCommentExceptionOnRemove() {

string xls = "in.xlsx";

ExcelPackage theExcel = new ExcelPackage(new FileInfo(xls), true);

ExcelRangeBase cell;
ExcelComment cmnt;
ExcelWorksheet ws = theExcel.Workbook.Worksheets[1];

foreach (string addr in "B4 B16".Split(' ')) {
cell = ws.Cells[addr];
cmnt = cell.Comment;

try {
ws.Comments.Remove(cmnt);
} catch (Exception ex) {
Assert.Fail("Exception while removing comment at " + addr + ": " + ex.Message);
}
}

}

```
After initial investigation, the problem seems to be in CellStore<T>.Delete, because the content of _commentsStore gets corrupted immediately after the first call to ExcelCommentCollection.Remove.

Same code referencing EPPlus 4.0.5 works fine.

Comments: Fixed in changeset 33392c36678d