Fixed the output of empty attributes, Daniel.
diff --git a/tree.c b/tree.c
index 5892a4e..1447855 100644
--- a/tree.c
+++ b/tree.c
@@ -2307,6 +2307,8 @@
 	xmlBufferWriteCHAR(value);
 	xmlBufferWriteChar("\"");
 	free(value);
+    } else  {
+	xmlBufferWriteChar("=\"\"");
     }
 }