POP3 mail add-on: fix fetching mail bodies without limit

* "No limit set" is signaled by a negative value in fFetchBodyLimit
  (cf. logic in POP3Protocol::SyncMessages())

src/add-ons/mail_daemon/inbound_protocols/pop3/POP3.cpp

@@ -82,7 +82,7 @@ POP3Protocol::POP3Protocol(const BMailAccountSettings& settings)
 
 	create_directory(fDestinationDir, 0777);
 
-	fFetchBodyLimit = 0;
+	fFetchBodyLimit = -1;
 	if (fSettings.HasInt32("partial_download_limit"))
 		fFetchBodyLimit = fSettings.FindInt32("partial_download_limit");
 }