Processor yield NPE under some circonstancies

### Questions

When using IntelliJ > 2020.2.4 the build fails with NPE in the CodeGenProcessor.
This sound very much like an intelliJ issue however their investigation seem to aim for a lack of robustness in some processor implementations.
Here is the ticket I filled in at IntelliJ' support : https://youtrack.jetbrains.com/issue/IDEA-258659
This other ticket may be of interest too: https://youtrack.jetbrains.com/issue/IDEA-257871

### Version 3.5.3

### Context

Problem ocurred while uprading from IntelliJ 2020.2.4 to 2020.3

### Do you have a reproducer?

The following sample project builds againts intelliJ 2020.2.4 and not against 2020.3

* https://github.com/ngmip/IDEA-258659

### Steps to reproduce

1. clone repo
2. build -> rebuild project

### Extra

* windows 10 pro
* oracle jdk8u201
* For those who are looking for a workround, in the link I provided above, they explained how to configure the `-Djps.track.ap.dependencies=false` flag, this worked for me.

Commencez par CodeGenProcessor et le reproducer IDEA-258659 associé. Reconstruisez le projet d’exemple avec IntelliJ 2020.2.4 et 2020.3 en utilisant JDK 8 afin de confirmer quand le NPE se produit, puis comparez le comportement du processeur avec les rapports IntelliJ. La tâche est terminée lorsque le processeur n’échoue plus avec un NPE dans la configuration de build signalée.

Rédigé par le modèle d'indexation à partir du texte de l'issue.