'None' hard-coded in /templates/plugins/fields/edit/edit-multiselect.vm : should be internationalized

When a custom field is using a "Multi Select" type and filed is not required, a choice is added with value -1 and label "None". The label part is not properly internationalized.

The 'None' string is hard coded in the velocity template /templates/plugins/fields/edit/edit-multiselect.vm. It should get the i18n string instead.

Changing line 10 of /templates/plugins/fields/edit/edit-multiselect.vm to read

        <option value="-1"#if (!$selectedValues || $selectedValues.empty || $selectedValues.contains("-1")) selected #end>${i18n.getText('common.words.none')}</option>

fixes this.