Commented Unassigned: Worksheet.Dimension.End can report incorrect number of columns and/or rows [15109]

When reading certain xlsx files, EPPlus [changeset 461 (b0be4ad76772)] can sometimes report incorrect number of columns and / or possibly rows when using the following properties:

```
ExcelWorksheet.Dimension.End.Row
ExcelWorksheet.Dimension.End.Column;
```

This behavior __was not present__ in the 3.x version of the library.

I have attached two sample xlsx files for which this behavior can be observed. I have also attached a patch that solves the problem for columns only (note that this is just a quick and dirty change and there's probably a better way to handle this).

Test01.xlsx: The problem is caused by the fact that sheet1.xml definition contains one extra Worksheet/cols/col node that seems to be defining the style used for the rest of document, even though no data is present there:

```
<col min="27" max="16384" width="162.5703125" style="1"/>
```

Test02.xlsx: The problem found in Test01.xlsx is also present here, and on top of that, you can see that in some rows there are extra cells with no content, defined as follows:

```
<c r="AD3" s="4"/>
<c r="AE3" s="4"/>
```

For Test01.xlsx, EPPlus 4.x is reporting one extra column. For Test02.xlsx, EPPlus 4.x is reporting three extra columns.
Comments: Fixed in changeset e6b1c3ccf0fa