Add error hint

This exception is *also* raised, when no membership types have been configured yet, which can be very confusing. It cost me a two hours to figure out the real reason, and I have the nagging suspicion that this had happened to me before. I'm not too happy about the phrasing, but it would be good to have a reference to a potentially incomplete configuration. Thanks.

CRM/Member/Form/Membership.php

@@ -474,7 +474,7 @@ DESC limit 1");
     // Throw status bounce when no Membership type or priceset is present
     if (empty($this->allMembershipTypeDetails) && empty($priceSets)
     ) {
-      CRM_Core_Error::statusBounce(ts('You do not have all the permissions needed for this page.'));
+      CRM_Core_Error::statusBounce(ts("You either do not have all the permissions needed for this page, or the membership types haven't been fully configured."));
     }
     // retrieve all memberships
     $allMembershipInfo = [];