conversation: Split out message parsing

Current code would not check if messages are empty

      log_data->msg = g_strdup (line_split[1]);

While fixing that I noticed that GStrv's are being leaked so fix this too by moving this into a easier to validate function. This

• uses a new GStrv for every split
• g_strdups the string right before assigning it to ChattyLog
• g_auto frees the variables