Confusing message when copying resources from project's baseDir

When the project base dir is used as the origin path, the relativize in https://github.com/apache/maven-filtering/blob/dce786df4301dab6d51d1eab6bbb79e510327086/src/main/java/org/apache/maven/shared/filtering/DefaultMavenResourcesFiltering.java#L259 resolves to empty string, resulting in nothing being displayed path after "from" in the console:

```
Copying 118 resources from to target/generated-docs
```