refs #21148 [finc] icon mapping: handle missing property concatenateKeys in config

module/finc/src/finc/View/Helper/Root/Record.php

@@ -139,7 +139,10 @@ class Record extends \VuFind\View\Helper\Root\Record
                     ->StyleBasedIcons->{$this->iconMappingType}
             ) ? $this->iconConfig
                 ->StyleBasedIcons->{$this->iconMappingType}->toArray() : [];
-            $this->concatKeysForIconMapping = $this->iconConfig
+            $this->concatKeysForIconMapping = isset(
+                $this->iconConfig
+                    ->StyleBasedIcons->concatenateKeys
+            ) && $this->iconConfig
                 ->StyleBasedIcons->concatenateKeys ? true : false;
         }
     }