Description of problem:
if I e.g. install a new file to /usr/local/bin and run restorecon for it,
it segfaults after setting the context because
param b in function only_changed_user is 0.

Also, on system startup I get segfault errors when restorecon
fails for /tmp/.ICE-unix and other files.

Version-Release number of selected component (if applicable):
1.20.1-2

How reproducible:
always

Steps to Reproduce:
1. create a new file at almost any dir
2. run restorecon on it
3.
  
Actual results:
restorecon gets killed because it dereferences null pointer

Expected results:
showing that context was restored and exiting normally...

Additional info:
patch attached.  quickie fix, it just checks for null pointers,
works for me,...