Saving a workbook with richtext enabled gives an error on python > 3.9
When loading, and later saving again a richtext enabled workbook, I get a combination of the following errors (on python 3.10)
```
File "C:\...\lib\site-packages\openpyxl\cell\_writer.py", line 82, in etree_write_cell
text = r.name
AttributeError: 'TextBlock' object has no attribute 'name'
File "C:\...\lib\site-packages\openpyxl\xml\functions.py", line 86, in whitespace
if node.text != node.text.strip():
AttributeError: 'xml.etree.ElementTree.Element' object has no attribute 'strip'
```
While searching for the issue, I found that others ran into it as well:
[issue on google groups](https://groups.google.com/g/openpyxl-users/c/ztrHJwWwfRU)
I fixed the bug locally, and attached the diff below (I don't know if this is the correct workflow, but I could not find how else to do this, not used to mercurial).
[patch.diff](/uploads/51c920ebc0a90d1d6ced69f0e604a58a/patch.diff)
issue