inkex: RecursionError in specified_style
#### Summary:
I received a file from an extension user which contained a path element with no style attribute (defaults to a black fill). This path is within a group with a `fill attribute` set to `currentColor`. When the `specified_style` method is run on the path element, we get a recursion error.
#### Steps to reproduce:
Here is a simplified extension code
```
class SpecifiedStyleError(EffectExtension):
def effect(self):
# path1 is in a group with a "fill" attribute set to "currentColor"
# path1 has no style (defaults to black fill)
path = self.svg.getElementById('path1')
path.specified_style()
```
Run the simplified extension code on the attached svg file.
#### What happened?
```
Traceback (most recent call last):
File "[...]specified_style_error.py", line 33, in <module>
SpecifiedStyle().run()
File "[...]/inkex/base.py", line 250, in run
self.save_raw(self.effect())
File "[...]specified_style_error.py", line 29, in effect
path.specified_style()
[... recursion removed ...]
style = element.specified_style()
File "[...]/inkex/elements/_base.py", line 628, in specified_style
return Style.specified_style(self)
File "[...]/inkex/styles.py", line 470, in specified_style
cascaded = Style.add_inherited(cascaded, parent.specified_style())
File "[...]/inkex/styles.py", line 241, in add_inherited
ret[key] = parent[key]
File "[...]/inkex/styles.py", line 278, in __setitem__
_ = value.parse_value(self.element)
File "[...]/inkex/properties.py", line 104, in parse_value
return self._parse_value(self.value, element)
File "[...]/inkex/properties.py", line 338, in _parse_value
return super()._parse_value(value, element)
File "[...]/inkex/properties.py", line 262, in _parse_value
style = element.specified_style()
File "[...]/inkex/elements/_base.py", line 628, in specified_style
return Style.specified_style(self)
File "[...]/inkex/styles.py", line 465, in specified_style
cascaded = Style.cascaded_style(element)
File "[...]/inkex/styles.py", line 428, in cascaded_style
styles = list(element.root.stylesheets.lookup_specificity(element.get_id()))
File "[...]/inkex/elements/_svg.py", line 386, in stylesheets
for node in self.xpath("//svg:style"):
File "[...]/inkex/elements/_base.py", line 437, in xpath
return super().xpath(pattern, namespaces=namespaces)
File "src/lxml/etree.pyx", line 1594, in lxml.etree._Element.xpath
File "src/lxml/xpath.pxi", line 259, in lxml.etree.XPathElementEvaluator.__init__
File "src/lxml/xpath.pxi", line 131, in lxml.etree._XPathEvaluatorBase.__init__
File "src/lxml/xpath.pxi", line 55, in lxml.etree._XPathContext.__init__
File "src/lxml/extensions.pxi", line 76, in lxml.etree._BaseContext.__init__
RecursionError: maximum recursion depth exceeded while calling a Python object
```
#### What should have happened?
Method should return the style
Sample attachments:

#### Version info
Inkscape 1.3-alpha (7e65aeea18, 2023-05-15)
GLib version: 2.76.2
GTK version: 3.24.37
glibmm version: 2.66.6
gtkmm version: 3.24.7
libxml2 version: 2.10.4
libxslt version: 1.1.37
Cairo version: 1.17.8
Pango version: 1.50.14
HarfBuzz version: 7.3.0
OS version: Arch Linux
issue