[RN] Fix TypeError that getDefaultButtons is not a function

react/features/toolbox/defaultToolbarButtons.native.js

+export default undefined;

react/features/toolbox/defaultToolbarButtons.web.js

-/* @flow */
+// @flow
 
 import React from 'react';
-import _ from 'lodash';
 
 import { ParticipantCounter } from '../contact-list';
 import { openDeviceSelectionDialog } from '../device-selection';
-
-import {
-    InfoDialogButton,
-    openInviteDialog
-} from '../invite';
-
-import { VideoQualityButton } from '../video-quality';
-
+import { InfoDialogButton, openInviteDialog } from '../invite';
 import UIEvents from '../../../service/UI/UIEvents';
+import { VideoQualityButton } from '../video-quality';
 
 import ProfileButton from './components/ProfileButton';
 
 declare var interfaceConfig: Object;
 declare var JitsiMeetJS: Object;
 
-let buttons: Object = {};
+/**
+ * The cache of {@link getDefaultButtons()}.
+ */
+let defaultButtons: Object;
 
 /**
  * Returns a map of all button descriptors and according properties.
  *
- * @returns {*} - The maps of default button descriptors.
+ * @returns {Object} - The maps of default button descriptors.
  */
-function getDefaultButtons() {
-    if (!_.isEmpty(buttons)) {
-        return buttons;
+export default function getDefaultButtons() {
+    if (defaultButtons) {
+        return defaultButtons;
     }
 
-    buttons = {
+    defaultButtons = {
         /**
          * The descriptor of the camera toolbar button.
          */
         }
     };
 
-    Object.keys(buttons).forEach(name => {
-        const button = buttons[name];
+    Object.keys(defaultButtons).forEach(name => {
+        const button = defaultButtons[name];
 
         if (!button.isDisplayed) {
-            button.isDisplayed = () => !interfaceConfig.filmStripOnly;
+            button.isDisplayed = _isDisplayed;
         }
     });
 
-    return buttons;
+    return defaultButtons;
 }
 
-export default getDefaultButtons;
+/**
+ * The default implementation of the {@code isDisplayed} method of the toolbar
+ * button definition returned by {@link getDefaultButtons()}.
+ *
+ * @returns {boolean} If the user intarface is full i.e. not filmstrip-only,
+ * then {@code true}; otherwise, {@code false}.
+ */
+function _isDisplayed() {
+    return !interfaceConfig.filmStripOnly;
+}

react/features/toolbox/reducer.js

-/* @flow */
+// @flow
 
 import { ReducerRegistry } from '../base/redux';
 
             };
 
         case SET_TOOLBAR_BUTTON:
-            return _setButton(state, action);
+            return _setToolbarButton(state, action);
 
         case SET_TOOLBAR_HOVERED:
             return {
     });
 
 /**
- * Sets new value of the button.
+ * Reduces the redux action {@code SET_TOOLBAR_BUTTON} in the feature toolbox.
  *
- * @param {Object} state - Redux state.
- * @param {Object} action - Dispatched action.
+ * @param {Object} state - The redux state.
+ * @param {Object} action - The redux action of type {@code SET_TOOLBAR_BUTTON}.
  * @param {Object} action.button - Object describing toolbar button.
  * @param {Object} action.buttonName - The name of the button.
  * @private
  * @returns {Object}
  */
-function _setButton(state, { button, buttonName }): Object {
-    const buttons = getDefaultButtons();
-    const buttonDefinition = buttons ? buttons[buttonName] : null;
+function _setToolbarButton(state, { button, buttonName }): Object {
+    // XXX getDefaultButtons, defaultToolbarButtons, SET_TOOLBAR_BUTTON are
+    // abstractions fully implemented on Web only.
+    const buttons = getDefaultButtons && getDefaultButtons();
+    const buttonDefinition = buttons && buttons[buttonName];
 
     // We don't need to update if the button shouldn't be displayed
     if (!buttonDefinition || !buttonDefinition.isDisplayed()) {
-        return {
-            ...state
-        };
+        return state;
     }
 
     const { primaryToolbarButtons, secondaryToolbarButtons } = state;