Perspective doesn't factor in transforms correctly (regression)
#### Steps to reproduce:
* Open [inkscape-test-perspective.svg](/uploads/323c6ec6776a449e0b0c3097a448567d/inkscape-test-perspective.svg)
* Select the red shape and using shift key, select the black path
* Apply **Extension -> Modify Path -> Perspective**
#### What happened?
Shape is drawn somewhere outside selection and also shape is random, not what it should be.
This is due to the `transform="scale(0.26458333)"` applied to the red path (translate and presumably all transforms are affected).
| before | after |
| ------ | ------ |
|  |  [inkscape-test-perspective-result.svg](/uploads/8eb16835bf7adc3f89942fb762852a8a/inkscape-test-perspective-result.svg) |
#### What should have happened?
Expected result: Here is how it looks on older versions (or if the path was nudged before applying the extension.

#### Inkscape Version and Operating System:
- Inkscape Version: 1.0 (4035a4fb49, 2020-05-01)
- Operating System: Windows 10 Home (64 bit)
- Operating System version: 1909
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