fix (button-group): button vertical alignment now working in tablet (#3393)

use "horizontal" instead of falsy ""

Author: Arukuen

src/block/button-group/edit.js

@@ -77,7 +77,7 @@ const TOOLBAR_ALIGN_OPTIONS = ALIGN_OPTIONS.map( control => {
 const ALIGNMENT_CONTROLS_DESKTOP = [
 	{
 		title: __( 'Horizontal', i18n ),
-		value: '',
+		value: 'horizontal',
 	},
 	{
 		title: __( 'Vertical', i18n ),
@@ -134,7 +134,7 @@ const Edit = props => {
 	] )
 
 	let contentAlignControls = null
-	if ( attributes.buttonAlign === '' ) {
+	if ( attributes.buttonAlign === 'horizontal' ) {
 		contentAlignControls = ALIGN_OPTIONS
 	}
 	if ( deviceType === 'Tablet' || deviceType === 'Mobile' ) {

src/block/button-group/style.js

@@ -50,9 +50,10 @@ blockStyles.addBlockStyles( 'buttonAlign', [ {
 	valuePreCallback: value => {
 		if ( value === 'vertical' ) {
 			return 'column'
+		} else if ( value === 'horizontal' ) {
+			return 'row'
 		}
-
-		return 'row'
+		return value
 	},
 }, {
 	renderIn: 'edit',