Prevent hidden popup overlay

A hidden overlay was preventing interactions with the lower 356 pixels
in the popup view when there are zero notifications. It was also
preventing interactions with the 100 pixels above the notifications in
the case where there were two notifications, which obscured the `Send`
button.

The first problem was solved by ensuring the notification wrapper isn't
rendered when there are no notifications. The second problem was solved
by updating the notification wrapper style to avoid setting a height.

ui/app/components/app/multiple-notifications/index.scss

@@ -3,7 +3,6 @@
   display: flex;
   flex-direction: column;
   width: 472px;
-  height: 116px;
   position: absolute;
   bottom: 0;
   right: 0;
@@ -37,7 +36,6 @@
 }
 
 .home-notification-wrapper--show-all {
-  height: 356px;;
   justify-content: flex-end;
   margin-bottom: 0;
 

ui/app/components/app/multiple-notifications/multiple-notifications.component.js

@@ -18,21 +18,27 @@ export default class MultipleNotifications extends PureComponent {
 
     const notificationsToBeRendered = notifications.filter(notificationConfig => notificationConfig.shouldBeRendered)
 
-    return (<div
-      className={classnames(...classNames, {
-        'home-notification-wrapper--show-all': showAll,
-        'home-notification-wrapper--show-first': !showAll,
-      })}
-    >
-      { notificationsToBeRendered.map(notificationConfig => notificationConfig.component) }
+    if (notificationsToBeRendered.length === 0) {
+      return null
+    }
+
+    return (
       <div
-        className="home-notification-wrapper__i-container"
-        onClick={() => this.setState({ showAll: !showAll })}
+        className={classnames(...classNames, {
+          'home-notification-wrapper--show-all': showAll,
+          'home-notification-wrapper--show-first': !showAll,
+        })}
       >
-        {notificationsToBeRendered.length > 1 ? <i className={classnames('fa fa-sm fa-sort-amount-asc', {
-          'flipped': !showAll,
-        })} /> : null}
+        { notificationsToBeRendered.map(notificationConfig => notificationConfig.component) }
+        <div
+          className="home-notification-wrapper__i-container"
+          onClick={() => this.setState({ showAll: !showAll })}
+        >
+          {notificationsToBeRendered.length > 1 ? <i className={classnames('fa fa-sm fa-sort-amount-asc', {
+            'flipped': !showAll,
+          })} /> : null}
+        </div>
       </div>
-    </div>)
+    )
   }
 }