Enhanced static property setter to support setting to both undefined and null values

lib/class_builder.js

@@ -643,8 +643,9 @@ function attachStatic( ctor, members, base, inheriting )
             }
 
             // if a value was provided, this method should be treated as a
-            // setter rather than a getter
+            // setter rather than a getter (we *must* test using
-            if ( val )
+            // arguments.length to ensure that setting to undefined works)
+            if ( arguments.length > 1 )
             {
                 props[ 'public' ][ prop ] = val;
                 return context;

test/test-class_builder-static.js

@@ -362,9 +362,20 @@ var common    = require( './common' ),
         } )
     ;
 
-    Foo.$( 'foo', undefined );
+    // first check to ensure we can set the value to null
-    Foo.$( 'foo', val );
+    Foo.$( 'foo', null );
+    assert.strictEqual( Foo.$( 'foo' ), null,
+        "Static properties may be set to null"
+    );
 
+    // then undefined (this actually won't do anything)
+    Foo.$( 'foo', undefined );
+    assert.strictEqual( Foo.$( 'foo' ), undefined,
+        "Static properties may be set to undefined"
+    );
+
+    // then set back to a scalar
+    Foo.$( 'foo', val );
     assert.equal( Foo.$( 'foo' ), val,
         "Setting static property to undefined does not corrupt lookup process"
     );