Comment 62 for bug 818648

I guess hibernate does not work with encrypted swap, and encrypted swap partition is something unknown to gparted, but I can't see why it needs to be a special partition different from normal swap partition.

As a workaround you could use a regular unencrypted swap partition: Disable swap by swapoff, edit /etc/fstab to mount regular swap partition instead of encrypted, and re-partition the swap partition by gparted. And then reboot.