Use null catalog when catalog is empty in TableColumnTypeValidationTest

This aligns with other places in our production code where we only use the provided catalog value if it is not empty.
There has been a change in Postgres in how it handles catalog with empty value.
See pgjdbc/pgjdbc#3390

Author: filiphr

modules/flowable-app-rest/src/test/java/org/flowable/test/persistence/TableColumnTypeValidationTest.java

@@ -196,21 +196,18 @@ protected Map<String, String> internalGetColumnMetaData(String tableName) {
                 if (StringUtils.isNotEmpty(databaseTablePrefix)) {
                     prefixedTableName = databaseTablePrefix + "." + tableName;
                 }
-                String catalog = processEngine.getProcessEngineConfiguration().getDatabaseCatalog();
+
+                // If the configured catalog is empty, we use null.
+                // This is the same logic as in the other places where we retrieve metadata
+                // (e.g., AbstractSqlScriptBasedDbSchemaManager.isTablePresent(String tableName)).
+                String catalog = StringUtils.defaultIfEmpty(processEngine.getProcessEngineConfiguration().getDatabaseCatalog(), null);
                 String schema = processEngine.getProcessEngineConfiguration().getDatabaseSchema();
                 if (StringUtils.isNotEmpty(schema) && AbstractEngineConfiguration.DATABASE_TYPE_ORACLE.equalsIgnoreCase(databaseType)) {
                     schema = schema.toUpperCase(Locale.ROOT);
                 }
 
                 Map<String, String> columnNameToTypeMap = new HashMap<>();
 
-                if (StringUtils.isEmpty(catalog) &&
-                        (databaseType.equals(AbstractEngineConfiguration.DATABASE_TYPE_MSSQL)
-                         || databaseType.equals(AbstractEngineConfiguration.DATABASE_TYPE_MYSQL))
-                ) {
-                    catalog = null; // Otherwise SQL server errors out
-                }
-
                 ResultSet resultSet = databaseMetaData.getColumns(catalog, schema, prefixedTableName, null);
                 while (resultSet.next()) {
                     String columnName = resultSet.getString("COLUMN_NAME");