FIX: fixing empty string netwoer_config_id field on test credentials

src/modules/connection-test/connection-test.service.ts

@@ -99,6 +99,10 @@ export class ConnectionTestService {
       username,
     });
 
+    if (body.network_config_id == '') {
+      body.network_config_id = undefined;
+    }
+
     /********* CREATE CONNECTION *********/
     if (!connection_id) {
       const properties: DatabaseConnectionPropertiesDto = {