search Field disappears with option searchAlwaysOpen

## Expected Behavior
Search field should always be displayed when the option is set to "true"

## Current Behavior
Search field disappears as soon as "viewColumns" or "filter" are clicked

## Steps to Reproduce (for bugs)
https://codesandbox.io/s/muidatatables-custom-toolbar-forked-gc95n?file=/index.js
1. click on the e.g. "viewColumn" - Button

## Your Environment

| Tech | Version |
|--------------|---------|
| Material-UI | 4.12.3 |
| MUI-datatables | 3.7.8 |
| React | 16.9.0 |

Start with the linked CodeSandbox reproduction in index.js and inspect how the searchAlwaysOpen option interacts with the viewColumns and filter toolbar actions. Reproduce the disappearance, then verify that the search field remains displayed after clicking either control using the listed Material-UI, MUI-datatables, and React versions.

Written by the indexing model from the issue text.