[js] Support passing null as the named arguments when there are none.

src/vm/js/Compiler.nqp

@@ -231,8 +231,13 @@ class QAST::CompilerJS does DWIMYNameMangling does SerializeOnce {
 
         # We want to always have at leat 1 thing to pass as the named argument
         if @named || @named_groups == 0 {
-            @named_groups.push(Chunk.new($T_OBJ,'{' ~ nqp::join(',',@named_exprs) ~ '}', @named));
+            if @named_exprs == 0 {
+                @named_groups.push(Chunk.new($T_OBJ, 'null', []));
+            } else {
+                @named_groups.push(Chunk.new($T_OBJ,'{' ~ nqp::join(',',@named_exprs) ~ '}', @named));
+            }
         }
+
         if $cont {
             @groups[0].unshift($cont);
         }
@@ -318,8 +323,12 @@ class QAST::CompilerJS does DWIMYNameMangling does SerializeOnce {
 
                     my $default := self.as_js($_.default, :want($T_OBJ), :$cps);
                     @setup.push($default);
-                    $value := "(_NAMED.hasOwnProperty($quoted) ? $value : {$default.expr})";
+                    $value := "((_NAMED !== null && _NAMED.hasOwnProperty($quoted)) ? $value : {$default.expr})";
                 }
+                else {
+                    $value := "(_NAMED !== null ? $value : null)";
+                }
+
                 # TODO required named arguments and defaultless optional ones
 
                 if self.is_dynamic_var($_) {

src/vm/js/nqp-runtime/bootstrap.js

@@ -114,16 +114,16 @@ add_knowhow_how_method('new_type', function(ctx, _NAMED) {
   var HOW = this._STable.REPR.allocate(this._STable);
 
   /* See if we have a representation name; if not default to P6opaque. */
-  var repr_name = _NAMED['repr'] || 'P6opaque';
+  var repr_name = (_NAMED && _NAMED.repr) ? _NAMED.repr : 'P6opaque';
 
   /* Create a new type object of the desired REPR. (Note that we can't
      * default to KnowHOWREPR here, since it doesn't know how to actually
      * store attributes, it's just for bootstrapping knowhow's. */
   var type_object = (new reprs[repr_name]).type_object_for(HOW);
 
   /* See if we were given a name; put it into the meta-object if so. */
-  if (_NAMED['name']) {
-    HOW.__name = _NAMED['name'];
+  if (_NAMED && _NAMED.name) {
+    HOW.__name = _NAMED.name;
   } else {
     HOW.__name = null;
   }

src/vm/js/nqp-runtime/core.js

@@ -245,11 +245,11 @@ op.captureposarg = function(capture, i) {
 };
 
 op.capturehasnameds = function(capture) {
-  return Object.keys(capture.named).length == 0 ? 0 : 1;
+  return (!capture.named || Object.keys(capture.named).length == 0) ? 0 : 1;
 };
 
 op.captureexistsnamed = function(capture, arg) {
-  return capture.named.hasOwnProperty(arg) ? 1 : 0;
+  return (capture.named && capture.named.hasOwnProperty(arg)) ? 1 : 0;
 };
 
 op.capturenamedshash = function(capture) {