Ignore failure of locale.getdefaultlocale.

This was reported to be a problem with the en_NG (Nigerian English)
locale by Kayode Adesina and Olisemeka Omo.

http://seclists.org/nmap-dev/2012/q2/965
http://seclists.org/nmap-dev/2012/q3/270

The underlying Python bug is this:

http://bugs.python.org/issue6895

CHANGELOG

@@ -1,5 +1,8 @@
 # Nmap Changelog ($Id$); -*-text-*-
 
+o [Zenmap] Fixed a crash when using the en_NG locale: "ValueError:
+  unknown locale: en_NG" [David Fifield]
+
 o [NSE] Added http-get by Alex Weber. This script looks for a .git
   repository directory accesible over HTTP and extracts useful
   information from it.

zenmap/zenmapCore/I18N.py

@@ -106,9 +106,15 @@ def get_locales():
         if val:
             locales = val.split(":")
             break
-    loc, enc = locale.getdefaultlocale()
-    if loc is not None:
-        locales.append(loc)
+    try:
+        loc, enc = locale.getdefaultlocale()
+        if loc is not None:
+            locales.append(loc)
+    except ValueError:
+        # locale.getdefaultlocale can fail with ValueError on certain locale
+        # names; it has been seen with at least en_NG.
+        # http://bugs.python.org/issue6895
+        pass
     return locales
 
 def install_gettext(locale_dir):