Yes, it is possible to update a group without changing the password of the group. However to change any specific detail of the group you need to pass the updated details along with the remaining details of the group along with the new detail you wish to update. For example, If you want to update a group description and want to keep all the other details as it is, you can do so by sending the group object as below:
new Group("GUID_OF_GROUP", "PREVIOUS_GROUP_NAME", "GROUP_TYPE", "PASSWORD_OF_THE_GROUP", "PREVIOUS_ICON_VALUE", "NEW_DESCRIPTION_OF_THE_GROUP")
Also, once you set any specific details you would not be able to unset those values. For example: Once you set the description of the group, you cannot set it to an empty description.
We have created a GitHub issue for this. You can watch the issue here to stay updated.