Conversation: Fix bug not displaying "You joined the conversation"

Edited the getContactInteractionString function of the namespace interaction
to display properly the message when joining a chat.

Gitlab: #1889
Change-Id: Ic1d6780a4fe9b35c9ab8eeb8d9cec435b0321513

src/libclient/api/interaction.h

@@ -285,6 +285,9 @@ getContactInteractionString(const QString& authorUri, const ContactAction& actio
         }
         return QObject::tr("%1 was invited to join the conversation.").arg(authorUri);
     case ContactAction::JOIN:
+        if (authorUri.isEmpty()) {
+            return QObject::tr("You joined the conversation.");
+        }
         return QObject::tr("%1 joined the conversation.").arg(authorUri);
     case ContactAction::LEAVE:
         return QObject::tr("%1 left the conversation.").arg(authorUri);