Description of Problem:
While selecting a mouse in the GUI install, one must select a serial port
if the mouse is serial for the "next" button to become available. However,
if one then unselects the com port, the next button stays clickable...and
anaconda tracebacks if one clicks on it. 

Version-Release number of selected component (if applicable):


How Reproducible:
100%

Steps to Reproduce:
1. Do a GUI install
2. Select a serial mouse at the mouse selection screen
3. Select a com port
4. deselect the com port
5. hit next

Actual Results:
Traceback

Expected Results:
"next" greyed out again when com port is deselected

Additional Information:
attaching traceback