[Slider] marks type is invalid

[LorenzHenk]

The slider prop type and typescript type allows the value false for marks, but using this value will lead to the error "marks.map is not a function".

The problem seems to be here: https://github.com/mui-org/material-ui/blob/master/packages/material-ui/src/Slider/Slider.js#L386

Examining this code block, I was able to trigger the same error with the following properties as well: marks={true} step={null} (see here).
marks={true} step={null} is an invalid configuration, so it's ok to throw. But I think it should be checked explicitly and there should be a descriptive error message. Alternatively, the typescript and prop types can be adapted to not allow these two values together, see the expected behavior section for more information.

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

When supplying the prop marks={false}, the Slider component throws an error.

This also happens with marks={false} step={null}.

Expected Behavior 🤔

I should not be able to set false as value in the first place - it should be prohibited by prop types and typescript.

Alternative solutions:

• there should be some special behavior with marks={false}
  or
• it should fall back to the default value ([]).

Steps to Reproduce 🕹

https://codesandbox.io/s/material-demo-kg4fn

Steps:

1. set marks={false} on the Slider component

Context 🔦

Nothing special, just noticed this problem by accident.

Your Environment 🌎

Tech	Version
Material-UI	v4.8.3

[oliviertassinari]

@LorenzHenk Thanks for raising. I have no idea what would be the best fix here. The fix you have proposed sounds good. Maybe somebody else has a preference?