[2.0.5] Empty summary in TokenSource

Problem/Motivation

When token value is empty, settingsSummary() returns an non-empty array.

Proposed resolution

diff --git a/src/Plugin/UiPatterns/Source/TokenSource.php b/src/Plugin/UiPatterns/Source/TokenSource.php
index 0275bc96..baaf3d4a 100644
--- a/src/Plugin/UiPatterns/Source/TokenSource.php
+++ b/src/Plugin/UiPatterns/Source/TokenSource.php
@@ -146,6 +146,9 @@ class TokenSource extends SourcePluginBase {
    * {@inheritdoc}
    */
   public function settingsSummary(): array {
+    if (empty($this->getSetting('value'))) {
+      return [];
+    }
     return [
       $this->getSetting('value'),
     ];