Fix dereference before null check warning

null tcon is not likely in these paths in current
code, but obviously it does clarify the code to
check for null (if at all) before derefrencing
rather than after.

Reported by Coverity (CID 1042666)

Signed-off-by: Steve French <smfrench@gmail.com>
Acked-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Acked-by: Sachin Prabhu <sprabhu@redhat.com>