[RNMobile] Fix issues with gradients on Button Block and resetting th…

…emes (#23075)

* Fix issues with gradients on Button Block

* Reset to Defaults when clearing theme

* Add code comments

packages/block-library/src/button/edit.native.js

@@ -176,9 +176,9 @@ class ButtonEdit extends Component {
 
 	getBackgroundColor() {
 		const { backgroundColor, attributes, gradientValue } = this.props;
-		const { gradient, customGradient } = attributes;
+		const { customGradient } = attributes;
 
-		if ( customGradient || gradient ) {
+		if ( customGradient || gradientValue ) {
 			return customGradient || gradientValue;
 		}
 		const colorAndStyleProps = getColorAndStyleProps( attributes );

packages/editor/src/components/provider/index.native.js

@@ -24,6 +24,7 @@ import {
 import { withDispatch, withSelect } from '@wordpress/data';
 import { compose } from '@wordpress/compose';
 import { applyFilters } from '@wordpress/hooks';
+import { SETTINGS_DEFAULTS } from '@wordpress/block-editor';
 
 const postTypeEntities = [
 	{ name: 'post', baseURL: '/wp/v2/posts' },
@@ -107,6 +108,15 @@ class NativeEditorProvider extends Component {
 
 		this.subscriptionParentUpdateTheme = subscribeUpdateTheme(
 			( theme ) => {
+				// Reset the colors and gradients in case one theme was set with custom items and then updated to a theme without custom elements.
+				if ( theme.colors === undefined ) {
+					theme.colors = SETTINGS_DEFAULTS.colors;
+				}
+
+				if ( theme.gradients === undefined ) {
+					theme.gradients = SETTINGS_DEFAULTS.gradients;
+				}
+
 				this.props.updateSettings( theme );
 			}
 		);