[Pagination] clicking on "..." triggers onChange with page equals to null (v5)

[kykungz]

Clicking on ... triggers Pagination onChange with page equals to null. This behavior does not appear in v4.

So when migrating to v5, I need to add a safety check for page !== null before setting current page value.

• 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 😯

Clicking on ... triggers onChange with page equals to null.

Expected Behavior 🤔

Clicking on ... should not trigger any event since it is just a label. Otherwise we always need to check for page !== null on every controlled Pagination.

Steps to Reproduce 🕹

<Pagination
  count={20}
  page={page}
  onChange={(_, page) => {
    // Always need safety check for page !== null
    if (page !== null) {
      setPage(page);
    }
  }}
/>

https://codesandbox.io/s/reverent-sun-e2kwy?file=/src/Demo.tsx

Context 🔦

This behavior does not appear in v4, not sure if this is a new intended behavior, but having to check for null on every Pagination seems not very convenient.

Your Environment 🌎

`npx @mui/envinfo`

  System:
    OS: macOS 11.5.2
  Binaries:
    Node: 16.7.0 - /opt/homebrew/bin/node
    Yarn: 1.22.11 - /opt/homebrew/bin/yarn
    npm: 7.20.3 - /opt/homebrew/bin/npm
  Browsers:
    Chrome: 94.0.4606.71
    Edge: Not Found
    Firefox: 91.0.1
    Safari: 14.1.2
  npmPackages:
    @emotion/react: ^11.4.1 => 11.4.1
    @emotion/styled: ^11.3.0 => 11.3.0
    @mui/core:  5.0.0-alpha.49
    @mui/icons-material: ^5.0.1 => 5.0.1
    @mui/lab: ^5.0.0-alpha.49 => 5.0.0-alpha.49
    @mui/material: ^5.0.2 => 5.0.2
    @mui/private-theming:  5.0.1
    @mui/styled-engine:  5.0.1
    @mui/styles: ^5.0.1 => 5.0.1
    @mui/system:  5.0.2
    @mui/types:  7.0.0
    @mui/utils:  5.0.1
    @types/react: ^17.0.24 => 17.0.24
    react: ^17.0.2 => 17.0.2
    react-dom: ^17.0.2 => 17.0.2
    typescript: ^4.4.3 => 4.4.3

[michaldudak]

Thanks for the report. It shouldn't work like this indeed.