pay_node module corrupts menu router when used in conjunction with donate module

the pay_node module ends up corrupting the menu_router table when used in conjunction with the donate module.

This happens because the pay_node module form_alters the menu_path to be set to an empty string instead of un-setting the variable.

Because the variable is set to an empty string- when the form is submitted - a menu item is created in the menu router (by donate module) with the path set to an empty string.

Pay_node should un-set the menu_path rather than setting it to an empty string. This will ensure that the menu path cannot be changed on node-edit - but will ensure that the menu router is not corrupted.

Donate module should explicitly set the 'type' property for every form associated with a pay_node to be a MENU_CALLBACK - OR- pay_node should implement a menu_alter hook to eliminate the extra menu entries for pay forms associated with pay_nodes. (not sure if this should be donate's job or pay_node's job)