inbound_protocols/imap: Fix PVS V773

Fix IMAPProtocol::_CreateFolder() was exited
without releasing 'folder' pointer.

Change-Id: I80249694b7a977a220cfb0853b169bae83129f76
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2908
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

src/add-ons/mail_daemon/inbound_protocols/imap/IMAPProtocol.cpp

@@ -296,6 +296,7 @@ IMAPProtocol::_CreateFolder(const BString& mailbox, const BString& separator)
 	if (status != B_OK) {
 		fprintf(stderr, "Initializing folder %s failed: %s\n", path.Path(),
 			strerror(status));
+		delete folder;
 		return NULL;
 	}