[NTG-context] \setupfooter[color=red]: red color spills with float over next page

```Hi Hans,

the patch solves the issue. Thank you for the fast reply.```
```
With regard to Pablo’s question: When I would not use crop in the MWE,
apparently I would get the desired output indeed. However, in the situation I
was using the command to produce a document, I would need to crop some parts of
a figure. I should have been a little bit more clear on this, I guess.

Thanks again,

Benjamin
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