Null values inside #PreAuthorize giving error - spring

Question

I'm trying to check if the user has role "ADMIN" and if he is the project's creator before giving him access to change the project like this:
#PreAuthorize("hasRole('ROLE_ADMIN') and this.projectService.findById(#id).getAdmin().getUsername() == authentication.name")
#RequestMapping(value = "/projects/{id}", method = RequestMethod.PUT)
public ResponseEntity<?> doUpdateProject(#PathVariable("id") Long id, #RequestBody ProjectDto project)
throws InstanceNotFoundException, DuplicatedResourceException {
Project updatedProject = projectService.update(id, project.getName(), project.getDescription());
return ResponseEntity.ok(updatedProject);
}
This works, only allowing an admin to update the project if he is the owner. But I noticed that if I make the call to a non-existent project, I get a 500 Internal Server Error instead of a 404 Not Found:
Servlet.service() for servlet [dispatcherServlet] in context with path [/tasks-service] threw exception [Request processing failed; nested exception is java.lang.IllegalArgumentException: Failed to evaluate expression 'hasRole('ROLE_ADMIN') and this.projectService.findById(#id).getAdmin().getUsername() == authentication.name'] with root cause.
I think that it is because of pointing to a null value (projectService.findById(#id)) but even when checking if the value is null, using for example a ternary operator that returns "true" if the value is null, I keep getting the same error.
#PreAuthorize("hasRole('ROLE_ADMIN') and this.projectService.findById(#id) != null ? this.projectService.findById(#id)?.getAdmin().getUsername() == authentication.name : true")
My idea here is to "pass" the #PreAuthorize condition when the project ID specified does not exist in order to get a 404 error later, but the same internal error is happening.
What should I do to get a 404 Not Found in this case?