Warning with maven multi module projects for non-installed dependencies.

Given a maven multi module project for which a module depends an another module within the same multi module project and the other module has not been installed, the following warning is issued when doing `mvn spotless apply` or `mvn spotless check` (even without the `expandWildcardImports` option):

```
[WARNING] Could not resolve project dependencies for expandWildcardImports: Unable to resolve dependencies
```

To reproduce:

```
git clone https://github.com/pdeneve/spotless-expand-wildcard-imports-issue.git
cd spotless-expand-wildcard-imports-issue
git checkout warning
mvn spotless:apply
```

Spotless maven plugin version used = `3.5.1`