DBFlute Engine: ReplaceSchema additionalDrop on MySQL

[jflute]

always NullPointerException (><

public UnifiedSchema getAdditionalDropSchema(Map<String, Object> additionalDropMap) {
    final String url = getAdditionalDropUrl(additionalDropMap);
    final String catalog;
    if (Srl.is_NotNull_and_NotTrimmedEmpty(url)) {
        final DfUrlAnalyzerFactory factory = new DfUrlAnalyzerFactory(getBasicProperties(), url);
        final DfUrlAnalyzer analyzer = factory.createAnalyzer();
        catalog = analyzer.extractCatalog();
    } else {
        catalog = getDatabaseProperties().getDatabaseCatalog();
    }
    final Object obj = additionalDropMap.get("schema");
    if (obj == null) {
        if (!isDatabaseAsSchemaSpecificationOmittable()) {
            String msg = "The schema is required:";
            msg = msg + " additionalDropMap=" + additionalDropMap;
            throw new DfRequiredPropertyNotFoundException(msg);
        }
        return null;
    }
    final String schema = castToString(obj, "additionalDropMapList.schema");
    return UnifiedSchema.createAsDynamicSchema(catalog, schema);
}

(cannot return null)