Collect unmapped entries in dry-run mode

See museum-digital/importer#235

src/MDConcCurrencies.php

@@ -99,7 +99,8 @@ final class MDConcCurrencies implements MDImporterConcordanceListInterface {
             if (in_array($input, MDCurrenciesSet::CURRENCIES, true)) {
                 return $input;
             }
-            throw MDImporterMissingConcordance::setup("currency", $input);
+            MDImporterMissingConcordance::throw("currency", $input);
+            return "eu-EUR"; // Return default in dry-run mode
         }
 
         return self::CURRENCIES_LIST[$input];