[banshee/gtk3] GSettings: add a couple of null argument checking to the extractor

[Andrés Aragoneses <aaragoneses src gnome org>]

commit 4e0ce13285e8c5462e83c905a44781736bc75217
Author: Andres G. Aragoneses <knocte gmail com>
Date:   Mon Apr 1 07:23:53 2013 +0100

    GSettings: add a couple of null argument checking to the extractor
    
    These turned to be useful when implementing the previously committed bugfix.

 build/GSettingsSchemaExtractor.cs |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)
---
diff --git a/build/GSettingsSchemaExtractor.cs b/build/GSettingsSchemaExtractor.cs
index b597d97..b4ecc80 100644
--- a/build/GSettingsSchemaExtractor.cs
+++ b/build/GSettingsSchemaExtractor.cs
@@ -146,6 +146,10 @@ public class GSettingsSchemaExtractorProgram
 
     private static string GetGcType (Type type)
     {
+        if (type == null) {
+            throw new ArgumentNullException ("type");
+        }
+
         // gctypes to return taken from 
http://developer.gnome.org/glib/unstable/glib-GVariant.html#GVariantClass
 
         if (type == typeof (bool)) {
@@ -204,6 +208,10 @@ public class GSettingsSchemaExtractorProgram
 
         internal static GSettingsKey ExtractFromField (SchemaSet schemaSet, FieldInfo field)
         {
+            if (field == null) {
+                throw new ArgumentNullException ("field");
+            }
+
             object schema = field.GetValue (null);
             if (schema == null) {
                 throw new InvalidSchemaException (String.Format (