fix: add check for session existence before writing to session writeStream in message-handler (#843)

Author: NickOvt

lib/message-handler.js

@@ -2102,7 +2102,7 @@ class MessageHandler {
         let { sourceUid, existsEntries, mailboxData, removeEntries, targetData, destinationUid } = data;
 
         // Show Expunged
-        if (sourceUid.length && options.showExpunged) {
+        if (options.session && sourceUid.length && options.showExpunged) {
             options.session.writeStream.write({
                 tag: '*',
                 command: String(options.session.selected.uidList.length),
@@ -2217,7 +2217,7 @@ class MessageHandler {
                 modseq: newModseq
             });
 
-            if (options.showExpunged) {
+            if (options.session && options.showExpunged) {
                 options.session.writeStream.write(options.session.formatResponse('EXPUNGE', messageUid));
             }
         }