Remove the code on opportunity onload function:
and replace with the following code
list: wn.model.get("Communication", {"parenttype":"Opportunity","parent":
this.frm.doc.name}),
so your code look like:
cur_frm.communication_view = new wn.views.CommunicationList({
list: wn.model.get("Communication", {"parenttype":"Opportunity","parent":
this.frm.doc.name}),
parent: cur_frm.fields_dict.communication_html.wrapper,
doc: this.frm.doc,
recipients: this.frm.doc.contact_email
});
Regards