[5.0] Fix undefined variables in scss (#41567)

* Fix undefined variables in scss

* Fix undefined variables in scss

Author: Fedik

build/media_source/templates/administrator/atum/scss/_variables-dark.scss

@@ -8,8 +8,8 @@ $atum-colors-dark: (
 
 $link-hover-color-dark: lighten($light-blue, 20%);
 
+$form-select-indicator-dark:       url("../images/select-bg-dark.svg");
+$form-select-indicator-rtl-dark:   url("../images/select-bg-rtl-dark.svg");
 $form-select-bg-dark:              var(--template-bg-dark);
 $form-select-background-dark:      $form-select-indicator-dark no-repeat right center / $form-select-bg-size; // Used so we can have multiple background elements (e.g. arrow and feedback icon)
 $form-select-background-rtl-dark:  $form-select-indicator-rtl-dark no-repeat left center / $form-select-bg-size; // Used so we can have multiple background elements (e.g. arrow and feedback icon)
-$form-select-indicator-dark:       url("../images/select-bg-dark.svg");
-$form-select-indicator-rtl-dark:   url("../images/select-bg-rtl-dark.svg");

build/media_source/templates/administrator/atum/scss/vendor/bootstrap/_custom-forms.scss

@@ -1,3 +1,5 @@
+@import "../../variables-dark";
+
 // Custom Forms
 
 .custom-select {

build/media_source/templates/administrator/atum/scss/vendor/choicesjs/choices.scss

@@ -2,6 +2,7 @@
 
 // Atum Variables
 @import "../../variables";
+@import "../../variables-dark";
 
 @import "../../../../../../../../media/vendor/bootstrap/scss/variables";
 @import "../../../../../../../../media/vendor/bootstrap/scss/mixins";