MultiTenantHelper.getTenantId() method should NOT call UserManager.getPrincipal(), otherwise it cannot be called from a computed group

if MultiTenantHelper.getTenantId() is called from a computed group contribution class (through call to UserProfileService.getUserProfileDocument()) we get a StackoverflowException as it calls UserManager.getPrincipal() which calls UserManager.makePrincipal(). Computed groups are computed in UserManager.makePrincipal().