Do more checks when creating NeutralCultureRegionMap.

See issue #82.
No idea if this code makes any sense and maybe it will lead to other problems later.

Gu.Localization/Internals/Culture.cs

@@ -46,7 +46,9 @@ internal static class Culture
         private static readonly Dictionary<CultureInfo, RegionInfo> NeutralCultureRegionMap =
             AllCultures
                 .Where(x => x.IsNeutralCulture)
-                .Select(x => NameCultureMap[CultureInfo.CreateSpecificCulture(x.Name).Name])
+                .Select(x => CreateSpecificCultureOrDefault(x)?.Name)
+                .Where(x => x != null && NameCultureMap.ContainsKey(x))
+                .Select(x => NameCultureMap[x])
                 .Distinct(CultureInfoComparer.ByTwoLetterIsoLanguageName)
                 .ToDictionary(
                     x => x.Parent,
@@ -95,5 +97,25 @@ internal static bool IsInvariant(this CultureInfo culture)
         {
             return NameEquals(culture, CultureInfo.InvariantCulture);
         }
+
+        private static CultureInfo CreateSpecificCultureOrDefault(CultureInfo neutral)
+        {
+            if (neutral == null ||
+                !neutral.IsNeutralCulture)
+            {
+                return null;
+            }
+
+            try
+            {
+                // try-catch swallow here as CreateSpecificCulture does parsing of the name.
+                // don't know if there is a 
+                return CultureInfo.CreateSpecificCulture(neutral.Name);
+            }
+            catch
+            {
+                return null;
+            }
+        }
     }
 }