[FIX] stock: mutation of the context

If the method do_enter_transfer_details is called form the new API, the context
is a frozendict and can not be updated and the previous code would crash.

Copying it before updating.

Closes #9872

addons/stock/stock.py

@@ -1406,7 +1406,8 @@ class stock_picking(osv.osv):
     def do_enter_transfer_details(self, cr, uid, picking, context=None):
         if not context:
             context = {}
-
+        else:
+            context = context.copy()
         context.update({
             'active_model': self._name,
             'active_ids': picking,