simplify logic and improve readability

function was only used in one place and only indirectly tested, so it could be inlined, which also makes the test for null and the extra variable allocation unnecessary

lib/TemplateSwitcher.php

@@ -65,7 +65,7 @@ class TemplateSwitcher
     }
 
     /**
-     * get currently loaded template
+     * get user selected template or fallback
      *
      * @access public
      * @static
@@ -73,8 +73,10 @@ class TemplateSwitcher
      */
     public static function getTemplate(): string
     {
-        $selectedTemplate = self::getSelectedByUserTemplate();
-        return $selectedTemplate ?? self::$_templateFallback;
+        if (array_key_exists('template', $_COOKIE) && self::isTemplateAvailable($_COOKIE['template'])) {
+            return $_COOKIE['template'];
+        }
+        return self::$_templateFallback;
     }
 
     /**
@@ -104,19 +106,4 @@ class TemplateSwitcher
         error_log('template "' . $template . '" is not in the list of `availabletemplates` in the configuration file');
         return false;
     }
-
-    /**
-     * get the template selected by user
-     *
-     * @access private
-     * @static
-     * @return string|null
-     */
-    private static function getSelectedByUserTemplate(): ?string
-    {
-        if (array_key_exists('template', $_COOKIE) && self::isTemplateAvailable($_COOKIE['template'])) {
-            return $_COOKIE['template'];
-        }
-        return null;
-    }
 }