[js] Fix bugs after null -> Null changes.

Author: pmurias

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

@@ -81,7 +81,7 @@ op.loadbytecode = function(ctx, file) {
   }
 
   var loadFrom;
-  if (ctx && (loadFrom = ctx.lookupDynamic('$*LOADBYTECODE_FROM'))) {
+  if (ctx && ((loadFrom = ctx.lookupDynamic('$*LOADBYTECODE_FROM')) !== Null)) {
   } else {
     loadFrom = module;
   }

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

@@ -438,7 +438,7 @@ class BinaryWriteCursor {
       case REFVAR_VM_ARR_VAR:
         this.varint(ref.array.length);
         for (var i = 0; i < ref.array.length; i++) {
-          this.ref(ref.array[i]);
+          this.ref(ref.array[i] || Null);
         }
         break;
       case REFVAR_VM_HASH_STR_VAR: