Fix menu bg undefined for the light theme

Author: dodo920306

src/main/webapp/css/select2-theming-patch.css

@@ -10,7 +10,7 @@
 .select2-container--bootstrap4 .select2-dropdown.select2-dropdown--below {
   border: 1px solid var(--input-border);
   box-shadow: 0 0 0 .2rem rgba(0, 123, 255, 0.25);
-  background-color: var(--menu-bg-color);
+  background-color: var(--input-color);
 }
 
 .select2-container--bootstrap4 .select2-search, .select2-search--dropdown .select2-search__field {
@@ -39,4 +39,4 @@
 
 .select2.select2-container.select2-container--bootstrap4 {
   width: 100% !important;
-}
+}