fix wrong view model

            <field name="act_window" ref="view_membership_tree" />

        </record>

        <record model="ir.ui.view" id="membership_period_view_tree_editable">

            <field name="model">association.membership</field>

            <field name="model">association.membership.period</field>

            <field name="type">tree</field>

            <field name="priority" eval="20" />

            <field name="name">membership_period_tree_editable</field>