[FIX] account_asset: hide the button 'set_to_draft' on assets already started...

[FIX] account_asset: hide the button 'set_to_draft' on assets already started to be depreciated because it makes no sense to be able to do so

addons/account_asset/views/account_asset_views.xml

@@ -103,7 +103,7 @@
                     <button name="validate" states="draft" string="Confirm" type="object" class="oe_highlight"/>
                     <button type="object" name="compute_depreciation_board" string="Compute Depreciation" states="draft"/>
                     <button name="set_to_close" states="open" string="Sell or Dispose" type="object" class="oe_highlight"/>
-                    <button name="set_to_draft" states="open" string="Set to Draft" type="object" />
+                    <button name="set_to_draft" string="Set to Draft" type="object" attrs="{'invisible': ['|', ('entry_count', '!=', 0), ('state', '!=', 'open')]}"/>
                     <button name="%(action_asset_modify)d" states="open" string="Modify Depreciation" type="action"/>
                     <field name="state" widget="statusbar" statusbar_visible="draft,open"/>
                 </header>