#### Steps to reproduce - create two paths - have an unset fill and/or stroke for either/both paths - run Extensions->Generate from Path->Interpolate , with Interpolate Style checked - get attached warning: ``` Traceback (most recent call last): File "interp.py", line 283, in <module> Interp().run() File "C:\APP\Temp\inkscape_devel\share\inkscape\extensions\inkex\base.py", line 141, in run self.save_raw(self.effect()) File "interp.py", line 101, in effect if isgradient(sst['stroke']) and isgradient(est['stroke']): File "interp.py", line 99, in <lambda> isgradient = lambda x: x.startswith('url(#') AttributeError: 'NoneType' object has no attribute 'startswith' ``` Occurs in extensions at master. The current extensions for 1.1-dev still suffer from the issue below Version info in comments, including Inkscape 1.1-dev (dbb3dfc0c3, 2020-08-23, custom) Linux Mint 20 <details><summary> Old bug (fixed in extensions at master)</summary> - Windows 10, Inkscape 1.1-dev (0741f45, 2020-08-20) - run Extensions->Generate from Path->Interpolate - get attached warning: - after this the extension appears to execute - however, if the two objects have different color, then it appears that the color is not being interpolated .................................................. <pre> interp.py:115: SyntaxWarning: "is" with a literal. Did you mean "=="? if strokestyle is 'color': interp.py:125: SyntaxWarning: "is" with a literal. Did you mean "=="? if fillstyle is 'color': </pre> </details>