Explicity copy action context on board action

The context is implicitly copied by or operator when it is evaluated to false,
but we should ensure it's always copied as it's updated with action values
issue6336

review34771002

tryton/gui/window/view_board/action.py

@@ -17,9 +17,11 @@ _ = gettext.gettext
 class Action(SignalEvent):
 
     def __init__(self, attrs=None, context=None):
+        if context is None:
+            context = {}
         super(Action, self).__init__()
         self.name = attrs['name']
-        self.context = context or {}
+        self.context = context.copy()
 
         try:
             self.action = RPCExecute('model', 'ir.action.act_window', 'get',