fix error in pncconf when there is no preference file

the first time you run pncconf there is no preference file,
that caused an error and pncconf would not continue.

Author: c-morley

Diff for: src/emc/usr_intf/pncconf/pncconf.py

@@ -3071,6 +3071,7 @@ def __init__(self):
                 self.data[i] = int(self.widgets[cb].child.connect("activate", self.on_general_pin_changed,"parport",connector,"Opin",pin,True))
 
         # set preferences if they exist
+        link = short = False
         filename = os.path.expanduser("~/.pncconf-preferences")
         if os.path.exists(filename):
             match =  open(filename).read()
@@ -3080,7 +3081,6 @@ def __init__(self):
                 textbuffer.insert_at_cursor(match)
             except:
                 pass
-            link = short = False
             version = 0.0
             d = xml.dom.minidom.parse(open(filename, "r"))
             for n in d.getElementsByTagName("property"):