Extensions for adjusting color (like HSL) don't work on grouped objects.
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#### Summary:
<!-- Summarize the issue/suggestion concisely: -->
The HSL adjust extension doesn't work on grouped objects. It works for ungrouped objects or when "entering" a group and selecting objects inside the group. The same applies to all color extension
#### Steps to reproduce:
<!-- Describe what you did (step-by-step) so we can reproduce: -->
- open Inkscape
- create red box
- create green box
- group the two boxes
- open menu "Extensions > Color > HSL adjust"
- apply hue, saturation or lightness changes
#### What happened?
- nothing
#### What should have happened?
- change of hue, saturation or lightness of the grouped objects according to the chosen values
Sample attachments:
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#### Version Info:
```
- Inkscape Version: 1.0 (4035a4fb49, 2020-05-01)
- Operating System: openSuSE Tumbleweed
- Operating System version: Rolling Release (Kernel 5.6.14-1.1, GNOME 3.36.2)
```
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issue