fix(virtual-background): Check if virtual background is disabled on premeeting.

react/features/base/premeeting/components/web/PreMeetingScreen.js

     /**
      * The video track to render as preview (if omitted, the default local track will be rendered).
      */
-    videoTrack?: Object
+    videoTrack?: Object,
+
+    /**
+     * Array with the buttons which this Toolbox should display.
+     */
+    visibleButtons?: Array<string>
 }
 
 /**
      * @inheritdoc
      */
     render() {
-        const { name, showAvatar, showConferenceInfo, title, videoMuted, videoTrack } = this.props;
+        const { name, showAvatar, showConferenceInfo, title, videoMuted, videoTrack, visibleButtons } = this.props;
         const showSharingButton = allowUrlSharing();
 
         return (
                             <div className = 'toolbox-content-items'>
                                 <AudioSettingsButton visible = { true } />
                                 <VideoSettingsButton visible = { true } />
-                                <VideoBackgroundButton visible = { checkBlurSupport() } />
+                                { ((visibleButtons && visibleButtons.includes('select-background'))
+                                   || (visibleButtons && visibleButtons.includes('videobackgroundblur')))
+                                   && <VideoBackgroundButton visible = { checkBlurSupport() } /> }
                             </div>
                         </div>
                     </div>

react/features/prejoin/components/Prejoin.js

 import React, { Component } from 'react';
 
 import { getRoomName } from '../../base/conference';
+import { getToolbarButtons } from '../../base/config';
 import { translate } from '../../base/i18n';
 import { Icon, IconArrowDown, IconArrowUp, IconPhone, IconVolumeOff } from '../../base/icons';
 import { isVideoMutedByUser } from '../../base/media';
      * The JitsiLocalTrack to display.
      */
     videoTrack: ?Object,
+
+    /**
+     * Array with the buttons which this Toolbox should display.
+     */
+    visibleButtons: Array<string>
 };
 
 type State = {
             showConferenceInfo,
             showJoinActions,
             t,
-            videoTrack
+            videoTrack,
+            visibleButtons
         } = this.props;
 
         const { _closeDialog, _onDropdownClose, _onJoinButtonClick, _onOptionsClick, _setName, _showDialog } = this;
                 skipPrejoinButton = { this._renderSkipPrejoinButton() }
                 title = { t('prejoin.joinMeeting') }
                 videoMuted = { !showCameraPreview }
-                videoTrack = { videoTrack }>
+                videoTrack = { videoTrack }
+                visibleButtons = { visibleButtons }>
                 {showJoinActions && (
                     <div className = 'prejoin-input-area-container'>
                         <div className = 'prejoin-input-area'>
         hasJoinByPhoneButton: isJoinByPhoneButtonVisible(state),
         showCameraPreview: !isVideoMutedByUser(state),
         showConferenceInfo,
-        videoTrack: getLocalJitsiVideoTrack(state)
+        videoTrack: getLocalJitsiVideoTrack(state),
+        visibleButtons: getToolbarButtons(state)
     };
 }