Users should be forced to write a group/user name when using the "Send Message" gadget

Steps to reproduce:

• Login as a user or admin
• Write a message in the "Send Message" text field
• Select Group or User from the drop-down list
• Click "Share"

The message appears as being sent in the "Activity Stream", but in fact it is only visible to the user that sent it. Users should be forced to write a user/group name or the message should be automatically sent to the group that the user belongs to when selecting "Group" from the drop-down list.

Tested on Firefox 17.