Created attachment 600469 [details]
Here I created a empty system group 'sysgrp' (no system is associated to this) and UI is raising pop-up 'Are you sure you want to remove selected system from system group entered ?'

Description of problem:
I was trying to remove a system from a system group but with bulk action. So I selected the system and by pressing control, the right pane get activated. 

I selected the system group which was not associated to any system and click on remove. UI raised a pop-up:

Are you sure you want to remove the 1 selected system(s) from the system group(s) entered?

And on clicking 'yes', a success notification raised.

Version-Release number of selected component (if applicable):
katello-0.2.47-1.git.225.b3aa579.el6_3.noarch

How reproducible:
always

Steps to Reproduce:
1. Create a system group and do not asscoiate any system, keep it empty
2. Go to systems --> press ctrl --> select any registered systems 
3. This makes right pane active, select the created empty system group in step1
4. a pop-up appears and success notification raised
  
Actual results:
UI raised an option and success notification for removing a system from empty system group.

Expected results: 
Since the selected system is not associated to any system group, so user shouldn't be able to select the empty system groups from the drop down. Only group names with which selected system's are associates should be displayed under the filter box otherwise its will create a confusion.

Additional info: