5.6.2: JDBC Sampler initialization failure makes test fail without any visible error

### Expected behavior

I am trying to test different DB with JMeter 5.6.2 and I expect for the test to run without issues.

As example JDBC Connection Configuration for MSSQL is in the attached picture.

### Actual behavior

When I run the test, nothing happens. No logs are written, nothing seems to be executed, no users are running. But when I try to close jmeter I get an message saying that I cannot do that since there is a test running.

I enabled debug logs for jdbc execution but no extra logs are present.

When doing the same test in Jmeter 5.4.3 (see attached JDBC Connection Configuration for MSSQL) it works.

This does not happen for all types of DB. It works for mongodb, mysql, mariadb, but id does not work for postgresql and mssql.

I am using the same jar files for jdbc drivers put in lib folder of both versions of jmeter.

### Steps to reproduce the problem

1. Setup a test for MSSQL or Postgresql in Jmeter 5.6.2
2. Run the test -> nothing happens, no logs are generated but also no results.
3. Try to close jmeter -> error message popup saying that a test is running.
4. Repeat with MSSQL 5.4.3 -> test is running successfully.

### JMeter Version

5.6.2

### Java Version

java version 11.0.16.1

### OS Version

Microsoft Windows [version 10.0.19044.3693]