refs #18082 [finc] adjust setMultiPart

* prevent from reuse former saved values within handling of an other marc field

module/finc/src/finc/RecordDriver/SolrMarcFincTrait.php

@@ -1520,6 +1520,7 @@ trait SolrMarcFincTrait
                         // at least we found some identifier and text so increment
                         $i++;
                     }
+                    unset($text, $label, $suffix);
                 }
             }
         }