[IMP] TO DISCUSS: added the dropzone when dragging on empty mail

Author: thjo-odoo

addons/mass_mailing_egg/static/src/themes/theme_wrapper.xml

@@ -12,7 +12,7 @@
             <div class="row">
                 <!-- TODO EGGMAIL to investigate if correct, but o_mail_wrapper will be responsible for the addition
                  of o_editable, which is necessary in `setup_editor_plugin` -->
-                <div class="col o_mail_no_options o_mail_wrapper_td bg-white oe_structure" t-out="html"/>
+                <div class="col o_mail_no_options o_mail_wrapper_td bg-white oe_structure oe_empty" t-out="html"/>
             </div>
         </div>
     </t>