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## Environment
**Liquibase Version**: 4.0.0

## Description
I am getting an NPE when I create a new FileSystemResourceAccessor(rootPath), with the following stack trace:

```
java.lang.NullPointerException
        at liquibase.Scope.getLog(Scope.java:278)
        at liquibase.resource.FileSystemResourceAccessor.addRootPath(FileSystemResourceAccessor.java:54)
        at liquibase.resource.FileSystemResourceAccessor.<init>(FileSystemResourceAccessor.java:36)
```

Looking at the Liquibase code, I see that SmartMap#get defines its result as a nullable, however, the Scope class does not check for null in this and other places.

## Steps To Reproduce
I'm running tests in my project, using liquibase-core:
Created this issue for tracking purposes, where you can also find the full stack trace: https://github.com/Treehopper/liquibase-lsp/issues/17

## Additional Context
In my project, I have to run scripts asynchronously. This, and the fact that the problem only occurs occasionally hints at a race-condition.


package liquibase;
import liquibase.configuration.LiquibaseConfiguration;
import liquibase.database.Database;
import liquibase.database.DatabaseConnection;
import liquibase.database.OfflineConnection;
import liquibase.database.jvm.JdbcConnection;
import liquibase.exception.UnexpectedLiquibaseException;
import liquibase.listener.LiquibaseListener;
import liquibase.logging.LogService;
import liquibase.logging.Logger;
import liquibase.logging.core.JavaLogService;
import liquibase.logging.core.LogServiceFactory;
import liquibase.resource.ClassLoaderResourceAccessor;
import liquibase.resource.ResourceAccessor;
import liquibase.servicelocator.ServiceLocator;
import liquibase.servicelocator.StandardServiceLocator;
import liquibase.ui.ConsoleUIService;
import liquibase.ui.UIService;