[gxml] Fixed throw error on invalid URI namespace

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit 2ce8bbd57741db4e25f553a1f4539521d016e417
Author: Daniel Espinosa <esodan gmail com>
Date:   Wed Nov 2 16:51:22 2016 -0600

    Fixed throw error on invalid URI namespace

 gxml/GomElement.vala      |    2 +-
 test/GomDocumentTest.vala |    4 ++++
 2 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/gxml/GomElement.vala b/gxml/GomElement.vala
index c7fdb69..14f62ba 100644
--- a/gxml/GomElement.vala
+++ b/gxml/GomElement.vala
@@ -334,7 +334,7 @@ public class GXml.GomElement : GomNode,
         nspn = _element.lookup_prefix ((node as DomAttr).namespace_uri);
         nsn = _element.lookup_namespace_uri (nspn);
         if (nspn != (node as DomAttr).prefix
-            && nsn != null && nsn != (node as DomAttr).namespace_uri)
+            && nsn != (node as DomAttr).namespace_uri)
           throw new DomError.NAMESPACE_ERROR
                   (_("Trying to add an attribute with a non found namespace URI"));
       }
diff --git a/test/GomDocumentTest.vala b/test/GomDocumentTest.vala
index 613cc3b..ca530d9 100644
--- a/test/GomDocumentTest.vala
+++ b/test/GomDocumentTest.vala
@@ -368,6 +368,10 @@ class GomDocumentTest : GXmlTest {
                                c.set_attribute_ns ("http://www.gnome.org/GXml2","gxml3:prop","val";);
                                assert_not_reached ();
                        } catch {}
+                       try {
+                               c.set_attribute_ns ("http://www.gnome.org/GXml3","gxml2:prop","val";);
+                               assert_not_reached ();
+                       } catch {}
                                var p = (c as DomElement).get_attribute_ns ("http://www.gnome.org/GXml2";, 
"prop");
                                assert (p == null);
                });