removed unused import and potential NPE

Author: chernser

jdbc-v2/src/main/java/com/clickhouse/jdbc/ConnectionImpl.java

@@ -2,7 +2,6 @@
 
 import com.clickhouse.client.api.Client;
 import com.clickhouse.client.api.ClientConfigProperties;
-import com.clickhouse.client.api.internal.ServerSettings;
 import com.clickhouse.client.api.metadata.TableSchema;
 import com.clickhouse.client.api.query.GenericRecord;
 import com.clickhouse.client.api.query.QuerySettings;

jdbc-v2/src/test/java/com/clickhouse/jdbc/JdbcIntegrationTest.java

@@ -5,15 +5,13 @@
 import com.clickhouse.client.ClickHouseServerForTest;
 import com.clickhouse.client.api.ClientConfigProperties;
 import com.clickhouse.client.api.internal.ServerSettings;
-import com.clickhouse.client.api.query.GenericRecord;
 import com.clickhouse.data.ClickHouseVersion;
 import com.clickhouse.logging.Logger;
 import com.clickhouse.logging.LoggerFactory;
 
 import java.sql.Connection;
 import java.sql.SQLException;
 import java.sql.Statement;
-import java.util.List;
 import java.util.Map;
 import java.util.Properties;
 
@@ -39,7 +37,9 @@ public Connection getJdbcConnection() throws SQLException {
 
     public Connection getJdbcConnection(Map<String, Object> propertiesMap) throws SQLException {
         Properties config = new Properties();
-        config.putAll(propertiesMap);
+        if (propertiesMap != null && !propertiesMap.isEmpty()) {
+            config.putAll(propertiesMap);
+        }
         return getJdbcConnection(config);
     }