[Xsltforms-support] better error message for multiple bind elements

[Leigh L K. Jr <lei...@xe...>]

Until the restriction on one bind element per node gets lifted, this 
helps you find the problem.
(Note that the restriction is peculiar to XSLTForms and is not part of 
XForms 1.1)

===================================================================
--- xsltforms.js    (xsltforms-dataisland-478)
+++ xsltforms.js    (working copy)
@@ -2340,7 +2340,7 @@
          var node = this.nodes[i];
          var bindid = Core.getMeta(node, "bind");
          if (bindid && this.element.id != bindid) {
-            XFProcessor.error(el, "xforms-binding-exception", "Two 
binds affect one node");
+            XFProcessor.error(el, "xforms-binding-exception", "Two 
binds affect one node: " + bindid + ", " + this.element.id);
          } else {
              Core.setMeta(node, "bind", this.element.id);

@@ -9241,6 +9241,7 @@
              if (arguments.length == 0) {
                  throw XPathCoreFunctionsExceptions.serializeNoContext;
              }
+                        if (!nodeSet[0]) return "";
              return Core.saveXML(nodeSet[0]);
          } ),