Intercompany

Issues Resolved

• [#10714] Fix to use an internal return type when doing intercompany stock transfers so that the history on the stock item will show the internal area.
• [#11345] Fix null object reference error when checking form mode after disposal.
• [#11345] Update back to back tab details on order line amendment. also unsubscribed from events on form close.
• [#13002] Fix when posting (purchase) invoices with different currencies and it would post an incorrect cost in the receiving company where it multiple the cost by the exchange rate. Further fix to also correctly post the tax value when it has been edited by the user.