'NoneType' object has no attribute 'parent' accessing the Fill property of an empty cell
*Created originally on Bitbucket by [memoselyk (Julian Trevino Mondragon)](https://bitbucket.org/%7Befae3a5a-0ded-4054-84e2-ae0ead0cc61d%7D/)* **Preconditions** Create an empty workbook and add only content to cell B2. **Steps to reproduce** 1. Open the workbook from precondition 2. Attempt to get the ```fill``` property of a cell obtained by iterating over rows from ```workbook.rows```. Sample snippet showing the failure, ``` #!python from openpyxl import load_workbook wb = load_workbook("test_file.xlsx", read_only=True) ws = wb.get_active_sheet() for ri, row in enumerate(ws.rows): for rc, cell in enumerate(row): col = chr(rc + ord('A')) try: print "%s, %d - %s" % (col, ri + 1, cell.fill) except Exception as err: print "%s, %d - ERROR %s" % (col, ri + 1, err) ``` **Observed results** Attemps to obtain the ```fill``` properties of cells A1, A2, B1 faill with error: ``` File "C:\Python27\lib\site-packages\openpyxl\cell\read_only.py", line 82, in fill _id = self.style_array.fillId File "C:\Python27\lib\site-packages\openpyxl\cell\read_only.py", line 65, in style_array return self.parent.parent._cell_styles[self._style_id] AttributeError: 'NoneType' object has no attribute 'parent' ``` **Expected results** I presume that such cells should, at least, return a None value instead of raising an exception.
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