[Dialog] Incorrect style on Dialog when maxWidth is set to false

Duplicates

• I have searched the existing issues

Latest version

• I have tested the latest version

Current behavior 😯

Setting maxWidth={false} on the Dialog component adds a MuiPaper-maxWidthFalse class to the paper div in the dialog. In the css for the generated class I see max-width: undefinedpx

Expected behavior 🤔

Setting maxWidth={false} should not add a class to the MuiPaper component which will leave the maxWidth property unset.

Steps to reproduce 🕹

Steps:

1. Navigate to https://codesandbox.io/s/simpledialog-material-demo-forked-u2nl0u
2. Click on the Open Simple Dialog button
3. Right click and inspect the Dialog paper and find the div with the MuiPaper-root class
4. The div also has a MuiPaper-maxWidthFalse class and inspecting the css reveals a max-width: undefinedpx property

Context 🔦

I was working on adding custom breakpoints to an application and testing that the new breakpoints worked as expected with the Dialog component. I noticed the max-width: undefinedpx in the diffs of my snapshots test and although it doesn’t seem to break anything for me, it still seemed like maybe worth fixing if it is a simple fix.

Your environment 🌎

`npx @mui/envinfo`

  Don't forget to mention which browser you used.
  Output from `npx @mui/envinfo` goes here.

[ZeeshanTamboli]

I think you mean paperWidthFalse class, not maxWidthFalse class. However, it is correct that the MuiDialog-paperWidthFalse class is applied. It’s just that max-width: undefinedpx style shouldn’t get applied when maxWidth={false} is passed.

[kmurgic]

I’m happy to make a PR with this change