Apply suggestions from code review

Thank you Marius! way better :)

Co-authored-by: Marius van den Beek <m.vandenbeek@gmail.com>

lib/galaxy/files/__init__.py

@@ -250,17 +250,13 @@ class ProvidesUserFileSourcesUserContext:
     def role_names(self) -> Set[str]:
         """The set of role names of this user."""
         user = self.trans.user
-        if user is None:
-            return set()
-        return user and set([ura.role.name for ura in user.roles])
+        return set(ura.role.name for ura in user.roles) if user else set()
 
     @property
     def group_names(self) -> Set[str]:
         """The set of group names to which this user belongs."""
         user = self.trans.user
-        if user is None:
-            return set()
-        return user and set([ugr.group.name for ugr in user.groups])
+        return set(ugr.group.name for ugr in user.groups) if user else set()
 
     @property
     def is_admin(self):