Add whitespace before add actions (#67835)

* Added empty string filter

* Changed operator in empty string filter

* Add space before add condition

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

x-pack/plugins/infra/public/alerting/metric_threshold/components/expression.tsx

@@ -288,6 +288,7 @@ export const Expressions: React.FC<Props> = (props) => {
         />
       </div>
 
+      <EuiSpacer size={'m'} />
       <div>
         <EuiButtonEmpty
           color={'primary'}